key CHRYSLER VOYAGER 2001 Service Manual

DTC P-Code Name of Code Limp-in MIL
71 P1797 Manual shift overheat No No
73 P1798 Worn out/burnt transmission fluid No No
74 P1799 Calculated Oil temperature in use No No
75 P1738 High temperature operation activated No No
76 P1739 Power up at speed No No
77 P1717 No communication with the MIC No No
78 P0600 Serial communication link malfunction No No
79 P1714 Low battery voltage Yes Yes
Yes (underlined) indicates that this DTC can take up to five minutes of problem identification before
illuminating the MIL.
3.3.7 DTC DESCRIPTIONS
Name of code:P1792(12) - Battery was Discon-
nected (Informational code Only)
When monitored:Whenever the key is in the
Run/Start position.
Set condition:This code is set whenever the
Transmission Control Module (TCM) is discon-
nected from battery power (B+) or ground. It will
also be set during the DRBIIItBattery Disconnect
procedure.
Theory of operation:A battery backed RAM
(Random Access Memory) is used to maintain some
learned values. When the battery B(+) is discon-
nected, the memory is lost. When the B(+) is re-
stored, this memory loss is detected by the TCM.
The code is set and the learned values are initial-
ized to known constants or previously learned val-
ues from EEPROM (Electronic Erasable Program-
mable Read Only Memory). This results in the
initialization of some parameters.
Transmission Effects:Loss of trouble code data.
Immediate limp-in mode if power is lost while
operating the vehicle. Normal operation is resumed
if the power is restored during the same key start.
Possible causes:
> Battery voltage removed from TCM
> TCM disconnected
> Dead Battery
> Low battery voltage during cranking
> Battery Disconnect by DRBIIItor MDS
> Bad TCM ground circuit.
Name of code:P1767(14) - Relay Output Always
On
When monitored:Ignition key is turned from off
position to run position and/or ignition key is
turned from crank position to run position.
Set condition:This code is set if the Transmission
Control Module (TCM) senses greater than 3 voltsat the Trans Relay Output (switched battery) ter-
minal of the TCM prior to the TCM energizing the
relay.
Theory of operation:The transmission control
relay is used to supply power to the solenoid pack
when the transmission is in normal operating
mode. When the relay is off, no power is supplied to
the solenoid pack and the transmission is in limp-in
mode. The relay output is fed back to the TCM
through pins 16 and 17. It is referred to as the
Trans Relay Output circuit or switched battery.
Transmission Effects:The MIL will illuminate
and the transmission system defaults to Logical
limp-in mode. Logical Limp-in mode results in the
same modes of operation as Relay Open Limp-in.
Since the relay is stuck9on9, the TCM can not open
the relay, and the TCM shifts to 2nd gear.
Possible causes:
> Relay failure (welded contacts)
> Short to battery in 12-volt supply and/or Trans-
mission Control Relay Output circuit(s)
> Short to voltage
> TCM connector problems
> TCM
Name of code:P1768(15) - Relay Output Always
Off
When monitored:Continuously
Set condition:This code is set when less than 3
volts are present at the Trans Relay Output
(switched battery) terminals at the Transmission
Control Module (TCM) when the TCM is energizing
the relay.
Theory of operation:The transmission control
relay is used to supply power to the solenoid pack
when the transmission is in normal operating
mode. When the relay is off, no power is supplied to
the solenoid pack and the transmission is in limp-in
mode. The relay output is fed back to the TCM
through pins 16 and 17. It is referred to as the
Trans Relay Output circuit or a switched battery.
5
GENERAL INFORMATION

After a controller reset (ignition key turned to the
run position or after cranking engine), the control-
ler energizes the relay. Prior to this the TCM
verifies that the contacts are open by checking for
no voltage at the switched battery terminals. After
the relay is energized, the TCM monitors the ter-
minals to verify that the voltage is greater than 3
volts.
Transmission Effects:The MIL illuminates and
the transmission system defaults to Relay Open
limp-in mode.
Possible causes:
> Relay failure (intermittent relay function caused
by oxidized or contaminated relay contacts)
> Short to ground or open circuit in the Transmis-
sion Control Relay circuit(s)
> TCM connector problem
> TCM
Name of code:P0725(18) - Engine Speed Sensor
Circuit
When monitored:Whenever the engine is run-
ning.
Set condition:This code is set when the engine
speed sensed by the Transmission Control Module
(TCM) is less than 390 RPM or greater than 8000
RPM for more that 2.0 seconds.
Theory of operation:The TCM uses either a
EATX RPM signal (simulated Crank Sensor signal)
or the TCM uses the Crank Postion Sensor signal to
calculate engine RPM depending on the engine
application. The signal supplied by the PCM and
uses a dedicated circuit is called the EATX RPM
Signal circuit. The Crank Position Sensor signal is
a spliced circuit from the engine Crank Position
Sensor. If the TCM interprets this signal to be out of
range when the engine is running (as reported by
the PCM over the bus) the code is set.
Transmission Effects:The MIL illuminates and
the transmission system defaults to Relay Open
limp-in mode.
Possible causes:
> Open or short in EATX RPM Signal circuit. (3.5L)
> Open or short in Crank Position Sensor Signal
circuit. (3.3L/3.8L)
> Open or short in Crank Position Sensor ground
circuit. (3.3L/3.8L)
> TCM and/or PCM connector problems
> TCM
> PCMName of code:P0716(19) - Bus Communication
with Engine Module
When monitored:Continuously with key on.
Set condition:If no PCI bus messages are received
from the Powertrain Control Module (PCM) for 10
seconds.
Theory of operation:The TCM communicates
with the PCM using the PCI bus. It relies on certain
information to function properly. The TCM contin-
uously monitors the PCI bus to check for messages
broadcast from the PCM.
Transmission Effects:Delayed 3-4 shifts. No
EMCC and early 3-4 shifts for a few minutes after
engine is started.
Possible causes:
> Open or shorted PCI bus circuit
> TCM
> PCM
Name of code:P1765(20) - Switched Battery
When monitored:Ignition key is turned from off
position to run position and/or ignition key is
turned from crank position to run position.
Set condition:This code is set if the Transmission
Control Module (TCM) senses voltage on any of the
pressure switch inputs prior to the TCM energizing
the relay.
Theory of operation:The transmission control
relay is used to supply power to the solenoid pack
when the transmission is in normal operating
mode. When the relay is off, no power is supplied to
the solenoid pack and the transmission is in a
limp-in mode. The relay output is fed back to the
TCM through pins 16 and 17. It is referred to as the
Trans Relay Output circuit or a switched battery.
Immediately after a controller reset (ignition key
turned to the run position or after cranking engine),
the TCM verifies that the relay contacts are open by
checking for no voltage at the switched battery
terminals. After this is verified, the voltage at the
Solenoid Pack pressure switches is checked. There
should be no voltage on the pressure switches at
this time. The TCM will then activate the relay.
Transmission Effects:The MIL illuminates and
the transmission system defaults to Relay Open
limp-in mode.
Possible causes:
> Short to battery on one or more pressure switch
sense circuits
> TCM connector problems
> TCM
6
GENERAL INFORMATION

Name of code:P1781(21) - OD Pressure Switch
Sense Circuit
When monitored:Whenever the engine is run-
ning.
Set condition:This code is set if the OD pressure
switch is open or closed at the wrong time in a given
gear (see chart below).
Theory of operation:The Transmission system
uses three pressure switches to monitor the fluid
pressure in the L-R, 2-4, and OD clutch circuits.
The pressure switches are continuously monitored
for the correct states in each gear as shown below.
Normal Pressure Switch States
Gear
L-R2-4OD
R OPOPOP
NCLOPOP
1st CL OP OP
2nd OP CL OP
3rd OP OP CL
4th OP CL CL
OP = switch is open
CL = switch is closed
Transmission Effects:Normal operation will be
experienced if no other codes are present. TCM will
ignore the code. Limp-in condition will only occur if
code P1781(21) is present with a code P0705(28).
Possible causes:
> If code P1791(35) is present, ignore code
P1781(21) and perform code P1791 diagnostic
procedures
> OD pressure switch sense circuit open or shorted
to ground between TCM and solenoid pack
> OD pressure switch sense circuit shorted to bat-
tery
> Solenoid pack
> Loose valve body bolts
> Plugged filter - internal transmission or torque
converter failure
> TCM
Name of code:P1782(22) - 2-4 Pressure Switch
Sense Circuit
When monitored:Whenever the engine is run-
ning.
Set condition:This code is set if the 2-4 pressure
switch is open or closed at the wrong time in a given
gear (see chart below).
Theory of operation:The Transmission system
uses three pressure switches to monitor the fluid
pressure in the L-R, 2-4, and OD elements. The
pressure switches are continuously monitored for
the correct states in each gear as shown below.
Normal Pressure Switch States
Gear
L-R2-4OD
R OPOPOP
NCLOPOP
1st CL OP OP
2nd OP CL OP
3rd OP OP CL
4th OP CL CL
OP = switch is open
CL = switch is closed
Transmission Effects: If the 2-4 pressure switch is
identified as closed in P or N, the code will imme-
diately be set and normal operation will be allowed
for that given key start. If the problem is identified
for 3 successive key starts, the transmission will go
into relay open limp-in mode. If the 2-4 pressure
switch is identified as being closed in 1st or 3rd gear
and was not identified as being closed in P or N,
then 2nd gear or 4th gear will be substituted for 1st
or 3rd gear depending on throttle angle and vehicle
speed. A short period of time after the gear substi-
tution, the transmission will return to normal op-
erating mode. If the transmission is shifted back
into 1st or 3rd gear through normal operation, and
the 2-4 pressure switch remains closed, 2nd or 4th
gear will be substituted briefly and then resume
normal operation. If four gear substitutions occur in
a given key start, the transmission will go into relay
open limp-in mode.
If the 2-4 pressure switch is open (indicating no
2-4 clutch pressure) in 2nd or 4th gear, the TCM
sets code P1782(22) and continues with normal
operation. The transmission will only go into relay
open limp-in mode if a code P0705(28) is also
present. If no 2-4 clutch pressure is present a speed
ratio code P0732(52) or P0734(54) will be set and
cause the limp-in condition.
Possible causes:
> If code P1791(35) is present, ignore code
P1782(22) and perform code P1791 diagnostic
procedures
> 2-4 pressure switch sense circuit open or shorted
to ground between TCM and solenoid pack
>
2-4 pressure switch sense circuit shorted to battery
> Solenoid pack
> Transmission overheated - Excessive regulator
valve leakage in valve body causing high line
pressure which results in 2-4 solenoid blow-off in
1st or 3rd gear. May require new valve body if it
happens only when hot.
> Loose valve body bolts
> Plugged filter - internal transmission or torque
converter failure
> TCM
7
GENERAL INFORMATION

Name of code:P1784(24) - L/R Pressure Switch
Sense Circuit
When monitored:Whenever the engine is run-
ning.
Set condition:This code is set if the L-R pressure
switch is either open or closed at the wrong time in
a given gear.
Theory of operation:The Transmission system
uses three pressure switches to monitor the fluid
pressure in the L-R, 2-4, and OD elements. The
pressure switches are continuously monitored for
the correct states in each gear as shown below.
Normal Pressure Switch States
Gear
L-R2-4OD
R OPOPOP
NCLOPOP
1st CL OP OP
2nd OP CL OP
3rd OP OP CL
4th OP CL CL
OP = switch is open
CL = switch is closed
Transmission Effects:If a set condition is identi-
fied, 1st gear and torque converter lock-up (EMCC)
will be inhibited. The vehicle will launch in 2nd
gear and shift normally through the gears without
allowing EMCC. If during the same key start, the
set condition is no longer valid, the transmission
will return to normal operation (1st and EMCC
available). A relay open limp-in will not occur unless
code P1784(24) is accompanied by a code P0705(28).
Possible causes:
> If code P1791(35) is present, ignore code
P1784(24) and perform code P1791(35) diagnos-
tic procedures> L-R pressure switch sense circuit open or shorted
to ground between TCM and solenoid pack
> L-R pressure switch sense circuit shorted to
battery
> Solenoid pack
> Valve body - solenoid switch valve stuck in LU
position. May be accompanied by a code
P1775(37)
> Loose valve body bolts
> Plugged filter - internal transmission or torque
converter failure
> TCM
Name of code:P0705(28) - Check Shifter Signal
When Monitored:Continuously with the key on.
Set Condition:3 occurrences in one key start of an
invalid PRNDL code which lasts for more than 0.1
second.
Theory of Operation:The C1 through C4 (T1, T3,
T41, and T42) sense circuits communicate the shift
lever position to the TCM. Each circuit is termi-
nated at the transmission with a switch. Each
switch can be either open or closed, depending on
the shift lever position. The TCM can decode this
information and determine the shift lever position.
Each shift lever position has a certain combination
of switches which will be open and closed, this is
called a PRNDL code. There are 4 switches, there-
fore: there are many possible combinations of open
and closed switches (codes). However, there are only
9 valid codes (8 for Autostick), one for each gear
position and three recognized between gear codes.
The remainder of the codes shouldnever occur,
these are called invalid codes. The following chart
shows the normal switch states for each shift lever
position.
TRS Park T1 Rev T2 N T2 OD T3 3/AS T3 L
T1 (C4) OP OP OP CL CL CL CL CL OP CL CL
T3 (C3) CL CL OP OP OP OP OP CL CL CL CL
T41 (C1) CL OP OP OP CL OP OP OP OP OP OP
T42 (C2) CL CL CL CL CL CL OP OP OP OP CL
8
GENERAL INFORMATION

Transmission Effects and possible causes:
Scenario 1)- All PRNDL lights stay illuminated
indefinitely in Park following a Key start.
> Wrong Part Number TCM for application
> TRS connector not plugged in
> C1 through C4 (T1, T3, T41, or T42) circuits are
either open, shorted to ground, or shorted to 12
volts.
> PCI bus failure (Open or shorted resulting in no
communication to BCM or Cluster)
> TRS
> TCM
> BCM
Scenario 2)-9P9is indicated following a key start
but all PRNDL lights illuminate in9N9following a
shift from9R9to9N9. If PRNDL lights illuminate in
9N9and shifter is moved directly into939or9L9
position without pausing in9OD9, then the9OD9
position shift schedule and electronic display will
indicate9OD9until the shifter is shifted into the
9OD9position and held for at least 3 seconds.
> Worn Manual Lever (Rooster Comb). Check for
heavy wearing by TRS switch contacts
> Intermittent C1 through C4 (T1, T3, T41 or T42)
circuits. Check for corrosion, terminal push-outs
or spread terminals at 60-way and/or TRS switch
10-way connector
> TRS
> TCM
> BCM
Scenario 3)- If the invalid code happened while
operating in the939or9L9position, then the939or
9L9shift schedule and electronic display will be
frozen (regardless of whether9OD9,939or9L9is
selected) until the shifter is moved to the9N9
position (all PRNDL lights will illuminate) and
then back to the9OD9position and held there for at
least 3 seconds in order to resume the normal9OD9
shift schedule and electronic display.
> Intermittent C1 through C4 (T1, T3, T41 or T42)
circuits. Check for corrosion, terminal push-outs
or spread terminals at 60-way and/or TRS con-
nector
> TRS
> TCM
> BCM
These same symptoms may occur without the
code P0705(28) getting set. It is possible that the
invalid code that was sensed by the TCM only
occurred once or twice during the given ignition key
start and/or did not last for longer than 0.1 second.Name of code:P0120(29) - Throttle Position Sen-
sor Signal
When monitored:Whenever the engine is run-
ning.
Set condition:This code is set if the throttle angle
goes out of range or if throttle angle changes
abruptly (ie: faster than the throttle body motion
could occur)
Theory of operation:The Transmission Control
Module (TCM) receives the throttle position signal
from the Throttle Position Sensor (TPS) through a
wire spliced into the TPS circuit to the PCM. The
TPS has a 5-volt pull up supplied from the Power-
train Control Module (PCM). The signal is checked
for out-of-range as well as an intermittent (exces-
sive signal changes).
Transmission Effects:Extremely erratic trans-
mission shifting with an intermittent TPS signal
just prior to setting the code. If the intermittent
does not last long enough to set the code, the
customer will say that the transmission violently
hunts between gears. The TCM will use a calcu-
lated throttle angle supplied by the PCM over the
PCI bus. If the PCI bus is unavailable, the TCM will
use a default throttle angle of 24 degrees for the key
start in which the code was set. The TCM will try to
use the TPS signal again on the next key start.
Possible causes:
> Open or shorted TPS signal and/or ground cir-
cuits
> TCM connector problems
> TPS or TPS connector (Check PCM DTC's)
> PCM
> TCM
Name of code:P1787(31) - OD Hydraulic Pressure
Test Failure
P1788(32) - 2-4 Hydraulic Pressure Test Failure
P1789(33) - OD/2-4 Hydraulic Pressure Test Failure
When monitored:In 1st, 2nd, or 3rd gear with
engine speed above 1000 RPM shortly after a shift
and every minute thereafter.
Set condition:Immediately after a shift into 1st,
2nd, or 3rd gear, with engine speed above 1000
RPM, the TCM momentarily turns on element
pressure to the 2-4 and/or OD clutch circuits to
identify that the appropriate pressure switch
closes. If the pressure switch does not close it is
tested again. If the switch does not close the second
time, the appropriate code is set.
Theory of operation:The Transmission Control
Module (TCM) tests the OD and 2-4 pressure
switches when they are off (OD and 2-4 are tested in
1st gear, OD in 2nd gear, and 2-4 in 3rd gear). The
test verifies that the switches are operational. The
TCM verifies that the switch closes when the cor-
9
GENERAL INFORMATION

responding element is applied. If a switch fails to
close, it is retested, If it fails the second test, the
code is set.
Transmission Effects:The MIL illuminates and
the transmission system defaults to Relay Open
limp-in mode.
Possible causes:
> Pressure switch sense circuit shorted to battery
between TCM and solenoid pack.
> Low line pressure
> Solenoid Pack
Name of code:P1791(35) - Loss Of Prime
When monitored:If the transmission is slipping
in any forward gear and the pressure switches are
not indicating pressure, a loss of prime test is run.
Set condition:If the transmission begins to slip in
any forward gear, and the pressure switch or
switches that should be closed for a given gear are
open, a loss of prime test begins. All available
elements (in 1st gear L-R, 2-4 and OD, in 2nd, 3rd,
and 4th gear 2-4 and OD) are turned on by the
Transmission Control Module (TCM) to see if pump
prime exists. The code is set if none of the pressure
switches respond. The TCM will continue to run the
loss of prime test until pump pressure returns.
Theory of operation:The loss of prime test is
used to prevent transmission defaults which can be
caused by a lack of pump prime.
Transmission Effects:Vehicle will not move or
transmission slips. Normal operation will continue
if pump prime returns.
Possible causes:
> Low transmission fluid level
> PRNDL indicates a valid OD code in the hydrau-
lic reverse position
> Transmission fluid filter clogged or damaged
> Transmission fluid filter improperly installed
(Bolts loose or O-ring missing)
> Oil pump - If a customer has a problem when the
transmission is cold whereby he shifts to reverse,
gets reverse, and then shifts to OD and does not
get OD (gets a neutral condition), and then can
not get reverse or OD for between 3-20 seconds,
replace the oil pump. High side clearance in the
oil pump will set a code 35. The pump will prime
upon start-up, but as the torque converter purges
air (drain down) the air will leak across the inner
rotor into the pump suction port and cause a loss
of prime right after the shift into OD. After 3- 20
seconds, pump prime will return and normal
operation will continue. The pump should be
replaced only after all other possible causes
above have been checked and verified.Name of code:P1790(36) - Fault Immediately
After Shift
When monitored:After a gear ratio error is
stored.
Set condition:This code is set if the associated
gear ratio code is stored within 1.3 seconds after a
shift.
Theory of operation:This code will only be stored
along with a 50 series code. If this code is set, it
indicates the problem is mechanical in nature.
When this code exists, diagnosing the transmission
should be based on the associated gear ratio code
and primarily mechanical causes should be consid-
ered.
Transmission Effects:None
Possible causes:
> Mechanical causes as listed under associated
gear ratio code.
Name of code:P1775(37) - Solenoid Switch Valve
Latched in TCC Position
When monitored:During an attempted shift into
1st gear.
Set condition:This code is set if three unsuccess-
ful attempts are made to get into 1st gear in one
given key start.
Theory of operation:The solenoid switch valve
(SSV) controls the direction of the transmission
fluid when the L-R/TCC solenoid is energized. The
SSV will be in the downshifted position in 1st gear,
thus directing the fluid to the L-R clutch circuit. In
2nd, 3rd, and 4th, it will be in the upshifted position
and directs the fluid into the torque converter
clutch (TCC).
When shifting into 1st gear, a special hydraulic
sequence is performed to ensure SSV movement
into the downshifted position. The L-R pressure
switch is monitored to confirm SSV movement. If
movement is not confirmed (the L-R pressure
switch does not close), 2nd gear is substituted for
1st.
Transmission Effects:Transmission will have no
1st gear (2nd gear will be substituted), and no
EMCC operation.
Possible causes:
> PRNDL indicates a valid OD code in the hydrau-
lic reverse position
> Valve body- - Solenoid valve stuck in TCC posi-
tion
> High idle speed
> Solenoid malfunction - L-R pressure switch will
not close
> L-R Pressure Switch Sense circuit shorted to
battery
10
GENERAL INFORMATION

Name of code:P0740(38) - Torque Converter
Clutch Control Circuit
When monitored:During Electronically Modu-
lated Converter Clutch (EMCC)
Set condition:
a) The transmission must be in EMCC, with the
input speed greater than 1750 RPM. The TCC/L-R
solenoid must achieve it's maximum duty cycle and
still not be able to pull the engine speed within 60
RPM of input speed.
b) If the transmission is in FEMCC and the engine
can slip the TCC by more than 100 RPM (Engine
speed - Input speed) for 10 seconds.
The code will be set if one of these event happens
three times at a throttle angle less than 30 degrees.
Theory of operation:When in 2nd, 3rd, or 4th
gear, the torque converter clutch (TCC) can be
locked when certain conditions are met. The TCC
piston is electronically modulated by increasing the
duty cycle of the L-R/TCC solenoid until the torque
converter slip difference (difference between engine
and turbine speed) is within 60 RPM. Then the
L-R/TCC solenoid is fully energized (FEMCC / 100%
duty cycle). Torque converter slip is monitored in
FEMCC to ensure adequate clutch capacity.
Transmission Effects:EMCC will still be avail-
able after code is set. MIL will illuminate after 5
minutes of accumulated slip in FEMCC. The trans-
mission will attempt normal operation (no limp-in)
even after the MIL is illuminated.
Possible causes:
> Worn pump bushing and/or failed torque con-
verter - both should be replaced during a rebuild
with code P0740(38) present
> Solenoid pack.
Name of code:P0750(41) - L-R Solenoid Circuit
P0755(42) - 2-4 Solenoid Circuit
P0760(43) - OD Solenoid Circuit
P0765(44) - UD Solenoid Circuit
When monitored:Ignition key is turned from off
position to run position and/or ignition key is
turned from crank position to run position, then
every 10 seconds thereafter, or when a speed ratio
or pressure switch error DTC is detected.
Set condition:All four solenoids are tested for
continuity continuously immediately upon start up
and during vehicle operation. For solenoids that are
currently energized, power is momentarily inter-
rupted, then reenergized. For solenoids that are not
currently energized, the solenoid is momentarily
energized, then deenergized. Under both situations,
if an inductive spike is not sensed by the Transmis-
sion Control Module (TCM) during the continuity
check, it is retested twice. If it fails the test the
third time, the appropriate code is set.
Gear UD OD Rev 2-4 L-R
Park X
Reverse X X
Neutral X
1st X X
2nd X X
3rd X X
4th X X
Theory of operation:Four solenoids are used to
control the friction elements (clutches). The conti-
nuity of the solenoids circuits are periodically
tested. Each solenoid is turned on or off depending
on it's current state. An inductive spike should be
detected by the TCM during this test. If no spike is
detected, the circuit is tested again to verify the
failure. In addition to the periodic testing, the
solenoid circuits are tested if a speed ratio or
pressure switch error occurs. In this case, one
failure will result in the appropriate code being set.
Transmission Effects:The MIL will illuminate
and the transmission goes into neutral if code is set
above 35 Km/h (22 MPH), limp-in mode when
vehicle speed is below 35 Km/h (22 MPH).
Possible causes:
> Open or shorted solenoid circuit(s) between TCM
and solenoid pack.
> Open ground circuit.
> TCM connector problems.
> Solenoid pack connector problem.
> Solenoid Pack.
> TCM
Name of code:P1776(47) - Solenoid Switch Valve
(SSV) Latched in L-R Position
When monitored:Continuously when doing par-
tial or full EMCC (PEMCC or FEMCC)
Set condition:If the transmission senses the L-R
pressure switch closing while performing PEMCC
or FEMCC. This code will be set after two unsuc-
cessful attempts to perform PEMCC or FEMCC.
Theory of operation:The solenoid switch valve
(SSV) controls the direction of the transmission
fluid when the L-R/TCC solenoid is energized. SSV
will be in the downshifted position in 1st gear, thus
directing the fluid to the L-R clutch circuits. In 2nd,
3rd, and 4th, the SSV will be in the upshifted
position and directs the fluid into the torque con-
verter clutch (TCC). When doing PEMCC or
FEMCC, the L-R pressure switch should indicate no
pressure if the SSV is in the TCC position. If the
L-R pressure switch indicates pressure while in
PEMCC or FEMCC, EMCC operation is aborted
and inhibited to avoid inadvertent application of
the L-R clutch. Partial EMCC will be attempted if
11
GENERAL INFORMATION

the L-R pressure switch does not indicate pressure.
A second detection of L-R pressure results in setting
the code.
Transmission Effects:At speeds above 72 Km/h
(45 MPH), EMCC is inhibited. Once speed falls
below 72 Km/h (45 MPH), the transmission will go
into relay open limp-in mode and the MIL will
illuminate.
Possible causes:
> Valve body - Solenoid valve stuck in L-R position
> Intermittent short to ground or open circuit in
L-R Pressure Switch Sense circuit (with code 24
only)
> Solenoid pack (with code P1784(24) only)
> TCM (with code P1784(24) only)
Name of Code:P1793(48) - Torque Reduction
(TRD) Link Communication Error
Note: The MIL may set on some engines (3.3L, 3.8L,
3.5L)
When Monitored:Whenever the engine is run-
ning
Set condition:This code is set when the TCM
sends multiple torque reduction messages to the
PCM and the TCM does not receive a response from
the PCM.
Theory of Operation:During high torque shifts
the TCM will send a message requesting that the
PCM reduce engine power until the shift is com-
pleted. This message is sent from the TCM to the
Powertrain Control Module across the Torque Man-
agement Request Sense Circuit. The PCM will
acknowledge the TCM request by sending a mes-
sage across the PCI bus within a specific amount of
time. The TRD Link communication is also tested
periodically for operation whenever the engine is
running and the vehicle is not moving with zero
degrees throttle.
Transmission Effects:Maximum throttle angle
used by TCM will be 54 degrees. As a result a
customer my complain about loss of performance or
of short shifting when driving aggressively.
Possible Causes:
> Sticky Throttle Position Sensor (TPS)
> Wiring or Connector problems in the Torque
Management Request Sense Circuit
> PCM
> TCM
Name of code:P0736(50) - Gear Ratio Error in
Reverse
P0731(51) - Gear Ratio Error in 1st
P0732(52) - Gear Ratio Error in 2nd
P0733(53) - Gear Ratio Error in 3rd
P0734(54) - Gear Ratio Error in 4th
P0715(56) - Input Speed Sensor Error
P0720(57) - Output Speed Sensor Error
P1794(58) - Speed Sensor Ground Error
When monitored:The transmission gear ratio is
monitored continuously while the transmission is in
gear.
Set condition:This code is set if the gear ratio is
not correct for a period of time.
± Codes 50 through 54 sets if the ratio of the
input RPM (Nt) to the output RPM (No) does
not match the given gear ratio.
± Code 56 sets if there is an excessive change in
input RPM in any gear
± Code 57 sets if there is an excessive change in
output RPM in any gear
± Code 58 sets after a TCM reset in neutral and
Nt/No equals a ratio of input to output of 2.50
A hard code sets within 3 seconds, an intermit-
tent code sets within 15 seconds.
Theory of operation:The transmission system
uses two speed sensors, one to measure input RPM
and one to measure output RPM. These inputs are
essential for proper transmission operation. There-
fore, the integrity of this data is verified through
the following checks:
1. When in gear, if the gear ratio does not compare
to a known gear ratio, the corresponding in-gear
trouble code is set (codes 50 through 54).
2. An excessive change in input or output speeds
indicating signal intermittent will result in
codes 56 and/or 57 being set.
3. After a TCM reset in neutral, observing erratic
output and input speed sensor signals indicates
a loss of the common speed sensors ground. This
sets a code 58.
Transmission Effects:The transmission will not
go into relay open limp-in mode until three gear
ratio error events occur in a given key start. This
allows for intermittent problems to correct them-
selves without opening the relay. However, if a gear
ratio error develops, a code is always set, but if the
condition corrects itself the transmission will con-
tinue without requiring the ignition key to be cycled
on and off. Many different events could occur given
the range of failures possible for codes 50 through
58. The following are a few examples:
± Codes 51, 52, 53, 54, 56, and 57 at speeds
above 72 Km/h (45 MPH) - The appropriate
code is set, EMCC is aborted and current gear
is maintained. If while still traveling above 72
Km/h (45 MPH), the gear ratio becomes valid
again, EMCC will reengage and normal oper-
ation will resume. If the gear ratio becomes
intermittent and recovers three times in a
given key start, the current gear will be main-
tained and EMCC inhibited, then the trans-
mission will go into relay open limp-in mode if
12
GENERAL INFORMATION

throttle is applied below 72 Km/h (45 MPH) or
at 35 Km/h (22 MPH) with closed throttle.
± Codes 51, 52, 53, 54, 56, and 57 (at speeds
between 35 and 72 Km/h (22 and 45 MPH) - If
one of these codes is set between 35 and 72
Km/h (22 and 45 MPH), the current gear will
be maintained until the gear ratio problem
corrects itself. If throttle is applied, the trans
will go to 2nd gear. If this happens and the
gear ratio problem goes away, normal opera-
tion will resume. If three gear ratio problems
are identified in a given key start, the current
gear will be frozen until throttle is applied.
The transmission will then go into relay open
limp-in mode with throttle applied at speeds
between 35 and 72 Km/h (22 and 45 MPH).
± Codes 51, 52, 53, 54, 56, and 57 (at speeds
below 35 Km/h (22 MPH) - If a gear ratio
problem is identified below 35 Km/h (22 MPH),
the transmission will immediately substitute
second gear for the current gear. If the gear
ratio problem goes away, normal operation will
resume. If three gear ratio problems are iden-
tified in a given key start, the transmission
will go into relay open limp-in mode.
Possible causes:
Code P0736(50) - Excludes geartrain failures which
should be obvious upon disassembly
> If code P1791(35) is also set, follow diagnostic
procedure for code P1791(35) first
> Valve body - #1 ball check or LR switch valve
sticking - may also set code P0731(51)
> Speed sensor or associated wiring
± may also set codes P0731(51), P0715(56), or
P0720(57)
> Failed or slipping LR clutch - may also set code
P0731(51)
> LR seal leakage (Intermittent no drive or re-
verse)
> Sticky LR accumulator seals (Intermittent no
drive or reverse)
> Failed reverse clutch (hard code)
± OD/Rev lip seal leakage
± Worn reaction shaft support seal rings
± Snap ring out of position
Code P0731(51) - Excludes geartrain failures which
should be obvious upon disassembly
> If code P1791(35) is also set, follow diagnostic
procedure for code P1791(35) first
> Valve body - #1 ball check or LR switch valve
sticking - may also set code P0736(56) or have no
Reverse
> Speed sensor or associated wiring - may also set
codes P0736(50), P0715(56), or P0720(57)> Failed or intermittent slipping UD clutch - may
also set P0732(52), or P0733(53)
± UD seal leakage (intermittent)
± Worn input clutch hub bushing (hard code at
heavy throttle)
± Sticky UD accumulator seals (intermittent)
± Worn reaction shaft support seal rings (hard
code at heavy throttle)
± Solenoid pack (UD pressure in 4th gear)
> Failed or slipping LR clutch - may also set code
P0736(56) or have no Reverse
± LR seal leakage (Intermittent)
± Sticky LR accumulator seals (Intermittent)
Code P0732(52) - Excludes geartrain failures which
should be obvious upon disassembly
> If code P1791(35) is also set, follow diagnostic
procedure for code P1791(35) first
> Failed or slipping 2-4 clutch - may also set code
P0734(54)
± 2-4 seal leakage (intermittent)
± Sticky accumulator seals (intermittent)
> Failed or intermittent slipping UD clutch - may
also set code P0731(51) and/or P0733(53)
± UD seal leakage (intermittent)
± Worn input clutch hub bushing (hard code at
heavy throttle)
± Sticky UD accumulator seals (intermittent)
± Worn reaction shaft support seal rings (hard
code at heavy throttle)
± Solenoid pack (UD pressure in 4th gear)
Code P0733(53) - Excludes geartrain failures which
should be obvious upon disassembly
> If code P1791(35) is also set, follow diagnostic
procedure for code P1791(35) first
> Failed or slipping OD clutch - may also set code
P0734(54)
± OD and Reverse inner and outer lip seal leak-
age (usually hard code)
± Sticky OD accumulator seals (intermittent)
± Worn reaction shaft support seal rings (hard
code at heavy throttle)
± Broken OD/UD tapered snap ring - (hard code
at heavy throttle)
> Failed or intermittent slipping UD clutch - may
also set code P0731(51) and/or P0732(52)
± UD seal leakage (intermittent)
± Worn input clutch hub bushing (hard code at
heavy throttle)
± Sticky UD accumulator seals (intermittent)
± Worn reaction shaft support seal rings (hard
code at heavy throttle)
13
GENERAL INFORMATION

then notice harsh bumps when the A/C clutch is
being cycled, but vehicle shudder will be elimi-
nated. After 35 OBDII (EURO STAGE III OBD)
warm-up starts or if the code is cleared, PEMCC
will be reactivated to see if shudder is still present.
If one shudder event occurs, the code will be reset.
Clearing the code and running battery disconnect
with the DRBIIItis the only way to reset the
shudder counter from 20 back to zero.
Transmission Effects:This code does not cause
the transmission to go into limp-in mode. However,
once the code is set, FEMCC to PEMCC operation
before the A/C clutch engagement will be disabled
for 35 OBDII (EURO STAGE III OBD) warm up
starts.
Possible causes:
> Degraded transmission fluid
> Wheels severely out of alignment
> Internal torque converter problem
Name of Code:P1799(74) - Calculated Oil Temper-
ature in Use
When Monitored:When ever the Engine is run-
ning.
Set condition:The code is set if any of the follow-
ing conditions exist for three consecutive key starts:
> The Temperature Sensor voltage is out of range
(below 0.07 volts or greater than 4.94 volts)
> If continuous erratic Temperature Sensor voltage
is sensed.
> The Temperature Sensor temperature stays be-
low 27C (80ÉF) for an extended period of time.
Theory of Operation:The TCM uses a Tempera-
ture Sensor to monitor the transmission sump tem-
perature. This temperature is used to determine
which shift schedule the TCM is to use. (See Trans-
mission Operation and Shift Scheduling at Various
Sump Temperatures in this diagnostic manual) If
the Temperature Sensor circuit fails to operate
properly the TCM will use the calculated oil tem-
perature routine found in prior model year TCM. If
this occurs for three consecutive key starts, the code
will be set. The TCM will then test the Temperature
Sensor circuit after every 35 OBDII (EURO STAGE
III OBD) warm-up starts. If the Temperature Sen-
sor circuit is OK, the Temperature Sensor data is
used in place of the Calculated Oil Temperature
data.
Transmission Effects:If the Temperature Sensor
indicates a temperature below -18C (0É F) or above
115C (240É F) at start up, The TCM compares the
calculated oil temperature to the indicated Temper-
ature Sensor oil temperature. If the calculated oil
temperature differs significantly from the Temper-
ature Sensor value, the calculated oil temperature
will be used for that key start.Possible Causes:
> Wiring or Connector problems in the transmis-
sion temperature sensor signal circuit.
> TRS
> TCM
Name of Code:P1738(75) - High Temperature
Operation Activated.
When Monitored:Whenever the engine is running.
Set Condition:Immediately once the Overheat
Shift Schedule is activated.
Theory of Operation:If the transmission oil tem-
perature rises above 115C (240ÉF), the overheat
shift schedule is activated refer to Transmission
Operation as a function of Transmission Oil Tem-
perature and the code is set. The DTC is an infor-
mation code only and is being set to aid the techni-
cian in determining root cause of a customer
driveability issue. The code is also intended to alert
the technician to determine if a cooling system
malfunction has occurred or if an additional trans-
mission air to oil cooler should be added to the
vehicle if the customer regularly drives in a manner
that overheats the transmission. Extended opera-
tion above 115C (240ÉF) will reduce the durability of
the transmission and should be avoided. Correcting
the cooling system malfunction or installing an
additional transmission oil cooler will improve
transmission durability especially for customers
who operate in city/construction stop and go traffic,
tow trailers regularly, drive aggressively in low gear
or drive regularly in mountainous areas.
Transmission Effects:Information only code. -
Overheat shift schedule was activated, no limp-in
condition occurs. 2nd gear partial EMCC above 40
Km/h (25 MPH), 3rd gear EMCC from 45-69 Km/h
(28-43 MPH), delayed 3-4 upshift at 69 Km/h (43
MPH), early 4-3 coastdown at 66 Km/h (41 MPH),
EMCC operation under all conditions above 40
Km/h (25 MPH) except at closed throttle or 1st gear.
Possible Causes:
± Transmission Overfilled with Oil
± Engine cooling fan failure
± Engine thermostat stuck closed
± Radiator corroded or packed with dirt
± Transmission Oil Cooler Plugged
± Customer driving pattern requires additional
transmission cooling
Name Of Code:P1739(76) - Power-Up at Speed
When Monitored:When TCM (transmission con-
trol module) initially powers-up.
Set Condition:If the TCM powers up while in the
9Drive9position and the vehicle is going above 32
Km/h (20 MPH), the code is set.
Theory of Operation:If a vehicle loses power to
the TCM, the vehicle will go to the 2nd gear mode
15
GENERAL INFORMATION