Rpm JEEP CHEROKEE 1995 Service Owner's Manual

DATA LINK CONNECTORÐPCM OUTPUT
Refer to the previous paragraphs on Data Link
ConnectorÐPCM Input for information.
EMR LAMPÐPCM OUTPUT
The EMR (SRI) lamp is not used for the 1995
model year.
FUEL PUMP RELAYÐPCM OUTPUT
The PCM energizes the fuel pump and the oxygen
sensor (O2S) heating element through the fuel pump
relay. Battery voltage is applied to the relay from the
ignition switch. The relay is energized when a
ground is provided by the PCM. Refer to Automatic
Shutdown Relay for additional information.
FUEL INJECTORSÐPCM OUTPUT
Six individual fuel injectors are used with the 4.0L
6-cylinder engine. Four individual fuel injectors are
used with the 2.5L 4-cylinder engine. The injectors
are attached to the fuel rail (Fig. 19).
The nozzle ends of the injectors are positioned into
openings in the intake manifold just above the intake
valve ports of the cylinder head. The engine wiring
harness connector for each fuel injector is equipped
with an attached numerical tag (INJ 1, INJ 2 etc.).
This is used to identify each fuel injector.
The injectors are energized individually in a se-
quential order by the powertrain control module
(PCM). The PCM will adjust injector pulse width by
switching the ground path to each individual injector
on and off. Injector pulse width is the period of time
that the injector is energized. The PCM will adjust
injector pulse width based on various inputs it re-
ceives.
During start up, battery voltage is supplied to the
injectors through the ASD relay. When the engine is
operating, voltage is supplied by the charging sys-
tem. The PCM determines injector pulse width based
on various inputs.
GENERATOR FIELDÐPCM OUTPUT
The powertrain control module (PCM) regulates the
charging system voltage within a range of 12.9 to
15.0 volts. Refer to Group 8A for charging system in-
formation.
GENERATOR LAMPÐPCM OUTPUT
IF EQUIPPED
If the powertrain control module (PCM) senses a
low charging condition in the charging system, it will
illuminate the generator lamp on the instrument
panel. For example, during low idle with all accesso-
ries turned on, the lamp may momentarily go on.
Once the PCM corrects idle speed to a higher rpm,
the lamp will go out. Refer to Group 8A, Battery/
Starting/Charging Systems for charging system infor-
mation.
IDLE AIR CONTROL (IAC) MOTORÐPCM OUTPUT
The IAC motor is mounted on the throttle body
(Figs. 20 or 21) and is controlled by the powertrain
control module (PCM).
Fig. 19 Fuel InjectorsÐTypical
Fig. 20 IAC MotorÐ4.0L Engine
Fig. 21 IAC MotorÐ2.5L Engine
JFUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION 14 - 27

coolant temperature drops to 98ÉC (208ÉF). Refer to
Group 7, Cooling Systems for more information.
The relay is located in the power distribution cen-
ter (PDC) (Fig. 25).
The electric radiator cooling fan is not used on YJ
models.
SCI TRANSMITÐPCM OUTPUT
SCI Transmit is the serial data communication
transmit circuit for the DRB scan tool. The power-
train control module (PCM) transmits data to the
DRB through the SCI Transmit circuit.
SHIFT INDICATORÐPCM OUTPUT
Vehicles equipped with manual transmissions have
an Up-Shift indicator lamp. The lamp is controlled by
the powertrain control module (PCM). The lamp illu-
minates on the instrument panel to indicate when
the driver should shift to the next highest gear for
best fuel economy. The PCM will turn the lamp OFF
after 3 to 5 seconds if the shift of gears is not per-
formed. The up-shift lamp will remain off until vehi-
cle stops accelerating and is brought back to range of
up-shift lamp operation. This will also happen if ve-
hicle is shifted into fifth gear.
The indicator lamp is normally illuminated when
the ignition switch is turned on and it is turned off
when the engine is started up. With the engine run-
ning, the lamp is turned on/off depending upon en-
gine speed and load.
SPEED CONTROLÐPCM OUTPUT
Speed control operation is regulated by the power-
train control module (PCM). The PCM controls the
vacuum to the throttle actuator through the speed
control vacuum and vent solenoids. Refer to Group
8H for speed control information.
TACHOMETERÐPCM OUTPUT
The powertrain control module (PCM) supplies en-
gine rpm values to the instrument cluster tachometer
(if equipped). Refer to Group 8E for tachometer infor-
mation.
TORQUE CONVERTER CLUTCH RELAYÐPCM
OUTPUT
ALL 2.5L 4 CYL. WITH 3-SPEED AUTO. TRANS
4.0L 6 CYL. YJ MODELS WITH 3-SPEED AUTO.
TRANS
The transmission mounted torque converter clutch
(TCC) solenoid is used to control the torque con-
verter. The solenoid is controlled through the power-
train control module (PCM) and by the TCC relay.
This relay is used only on vehicles equipped with a
3-speed automatic transmission.
An electrical output signal is sent from the PCM to
the TCC relay after the PCM receives information
from the vehicle speed, MAP, throttle position and
engine coolant temperature sensors. After the TCC
relay receives this necessary information, it will send
a signal to the torque converter clutch solenoid to
control the torque converter.
On YJ models the TCC relay is located in the en-
gine compartment, on the cowl panel and near the
battery (Fig. 26). On XJ models the TCC relay is lo-
cated in the power distribution center (PDC) (Fig.
25).
AIR CLEANER
The air cleaner assembly used on all models (Figs.
27 or 28) is open to ambient air. The blend air door
and vacuum motor that was used on engines of pre-
vious model years to supply heated air, is no longer
used. The air cleaner housing contains the engine air
cleaner element.
Fig. 25 PDCÐXJ Models
Fig. 26 TCC Relay LocationÐYJ Models
JFUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION 14 - 29

²The PCM adjusts ignition timing by increasing
and decreasing spark advance.
²The PCM operates the A/C compressor clutch
through the clutch relay. This happens if A/C has
been selected by the vehicle operator and requested
by the A/C thermostat.
The optional Extended Idle Switch is used to raise
the engine idle speed to approximately 1000 rpm.
This is when the shifter is in either the Park or Neu-
tral position. A rocker-type 2-wire switch (extended
idle switch) is mounted to the instrument panel. This
switch will supply a ground circuit to the powertrain
control module (PCM).The switch is available
only with 4.0L engine when supplied with the
optional police package.
CRUISE MODE
When the engine is at operating temperature, this
is a Closed Loop mode. At cruising speed, the power-
train control module (PCM) receives inputs from:
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal (in the distribu-
tor)
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Oxygen (O2S) sensor
Based on these inputs, the following occurs:
²Voltage is applied to the fuel injectors with the
PCM. The PCM will then adjust the injector pulse
width by turning the ground circuit to each individ-
ual injector on and off.
²The PCM monitors the O2S sensor input and ad-
justs air-fuel ratio. It also adjusts engine idle speed
through the idle air control (IAC) motor.
²The PCM adjusts ignition timing by turning the
ground path to the coil on and off.
²The PCM operates the A/C compressor clutch
through the clutch relay. This happens if A/C has
been selected by the vehicle operator and requested
by the A/C thermostat.
ACCELERATION MODE
This is an Open Loop mode. The powertrain control
module (PCM) recognizes an abrupt increase in
throttle position or MAP pressure as a demand for
increased engine output and vehicle acceleration. The
PCM increases injector pulse width in response to in-
creased throttle opening.
DECELERATION MODE
When the engine is at operating temperature, this
is an Open Loop mode. During hard deceleration, the
powertrain control module (PCM) receives the follow-
ing inputs.
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal (in the distribu-
tor)
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
If the vehicle is under hard deceleration with the
proper rpm and closed throttle conditions, the PCM
will ignore the oxygen sensor input signal. The PCM
will enter a fuel cut-off strategy in which it will not
supply battery voltage to the injectors. If a hard de-
celeration does not exist, the PCM will determine the
proper injector pulse width and continue injection.
Based on the above inputs, the PCM will adjust en-
gine idle speed through the idle air control (IAC) mo-
tor.
The PCM adjusts ignition timing by turning the
ground path to the coil on and off.
The PCM opens the ground circuit to the A/C
clutch relay to disengage the A/C compressor clutch.
This is done until the vehicle is no longer under de-
celeration (if the A/C system is operating).
WIDE OPEN THROTTLE MODE
This is an Open Loop mode. During wide open
throttle operation, the powertrain control module
(PCM) receives the following inputs.
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal (in the distribu-
tor)
During wide open throttle conditions, the following
occurs:
²Voltage is applied to the fuel injectors with the
powertrain control module (PCM). The PCM will
then control the injection sequence and injector pulse
width by turning the ground circuit to each individ-
ual injector on and off. The PCM ignores the oxygen
sensor input signal and provides a predetermined
amount of additional fuel. This is done by adjusting
injector pulse width.
²The PCM adjusts ignition timing by turning the
ground path to the coil on and off.
14 - 32 FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATIONJ

EXTENDED IDLE SWITCH TEST
OPTIONAL POLICE PACKAGE ONLY
OPERATION
The extended idle switch is used to raise the en-
gine idle speed to approximately 1000 rpm when the
shifter is in either the Park or Neutral position. A
rocker-type 2-wire switch (extended idle switch) is
mounted to the instrument panel.This switch is
available only with 4.0L engine when supplied
with the optional police package.
TESTING
The extended idle switch will control a ground cir-
cuit going to the powertrain control module (PCM).
When a ground signal (through this switch) has been
received at pin number 10 in the PCM, engine idle
speed will increase.
Bring the engine to normal operating temperature
and turn the extended idle switch to the ON position.
Engine speed should now increase to approximately
1000 rpm when the shifter is in either the Park or
Neutral position. If engine speed does not increase,
apply a good ground to pin number 10 at the PCM
using a small paper clip. Be careful not to damage
the wiring with the paper clip. If the engine speed
now increases, it can be assumed that the PCM is
functioning correctly. Check the instrument panel
mounted switch for a closed ground circuit when in
the ON position. If the engine speed will not increase
after applying a ground to pin number 10, replace
the PCM. Refer to Group 8W, Wiring Diagrams for
circuit and wiring information.
THROTTLE POSITION SENSOR (TPS) TEST
To perform a complete test of the sensor and its cir-
cuitry, refer to DRB scan tool and appropriate Pow-
ertrain Diagnostics Procedures manual. To test the
sensor only, refer to the following:
The throttle position sensor (TPS) can be tested
with a digital voltmeter. The center terminal of the
TPS is the output terminal (Figs. 38 or 39).
With the ignition key in the ON position, back-
probe the TPS connector. Check the TPS output volt-
age at the center terminal wire of the connector.
Check this at idle (throttle plate closed) and at wide
open throttle (WOT). At idle, TPS output voltage
should must be greater than 200 millivolts. At wide
open throttle, TPS output voltage must be less than
4.8 volts. The output voltage should increase gradu-
ally as the throttle plate is slowly opened from idle to
WOT.
TORQUE CONVERTER CLUTCH RELAY TEST
To test the relay only, refer to RelaysÐOperation/
Testing in this section of the group. To test the
torque converter clutch circuit and related compo-nents, refer to the appropriate Powertrain Diagnostic
Procedures manual for operation of the DRB scan
tool.
VEHICLE SPEED SENSOR TEST
To perform a complete test of the sensor and its cir-
cuitry, refer to DRB scan tool and appropriate Pow-
ertrain Diagnostics Procedures manual.
OXYGEN SENSOR (O2S) HEATING ELEMENT TEST
To perform a complete test of the O2S sensor (Fig.
40) and its circuitry, refer to DRB scan tool and ap-
propriate Powertrain Diagnostics Procedures manual.
To test the sensor only, refer to the following:
The oxygen sensor heating element can be tested
with an ohmmeter as follows:
With the sensor at room temperature 25 degrees C
(77 degrees F), disconnect the O2S sensor connector.
Connect the ohmmeter test leads across the white
wire terminals of the sensor connector. Resistance
should be between 5 and 7 ohms. Replace the sensor
if the ohmmeter displays an infinity (open) reading.
Fig. 38 TPS TestingÐ2.5L Engine
Fig. 39 TPS TestingÐ4.0L Engine
14 - 48 FUEL SYSTEM GENERAL DIAGNOSISJ

(8) Disconnect jumper wires from relay and 12 Volt
power source.
If continuity or resistance tests did not pass, re-
place relay. If tests passed, refer to Group 8W, Wiring
Diagrams for additional circuit information. Also re-
fer to the appropriate Powertrain Diagnostic Proce-
dures manual for operation of the DRB scan tool.
STARTER MOTOR RELAY TEST
Refer to Group 8A, Battery/Starting/Charging/Sys-
tem Diagnostics, for starter motor relay testing.
FUEL INJECTOR TEST
To perform a complete test of the fuel injectors and
their circuitry, refer to DRB scan tool and appropri-
ate Powertrain Diagnostics Procedures manual. To
test the injector only, refer to the following:
Disconnect the injector wire connector from the in-
jector. Place an ohmmeter on the injector terminals.
Resistance reading should be approximately 14.5
ohms61.2 ohms at 20ÉC (68ÉF). Proceed to the fol-
lowing Injector Diagnosis chart.When performing
the following tests from the chart, do not leave
electrical current applied to the injector for
longer than five seconds. Damage to injector
coil or internal injector seals could result.
FUEL SYSTEM PRESSURE TEST
Refer to the Fuel Delivery System section of this
group. See Fuel System Pressure Test.
ON-BOARD DIAGNOSTICS (OBD)
The powertrain control module (PCM) has been
programmed to monitor many different circuits of the
fuel injection system. If a problem is sensed in a
monitored circuit often enough to indicate an actual
problem, a Diagnostic Trouble Code (DTC) is stored.
The DTC will be stored in the PCM memory for even-
tual display to the service technician. If the problem
is repaired or ceases to exist, the PCM cancels the
DTC after 51 engine starts.Certain criteria must be met for a diagnostic trou-
ble code (DTC) to be entered into PCM memory. The
criteria may be a specific range of engine rpm, engine
temperature and/or input voltage to the PCM.
It is possible that a DTC for a monitored circuit
may not be entered into memory even though a mal-
function has occurred. This may happen because one
of the DTC criteria for the circuit has not been met.
Example: assume that one of the criteria for the
MAP sensor circuit is that the engine must be oper-
ating between 750 and 2000 rpm to be monitored for
a DTC. If the MAP sensor output circuit shorts to
ground when the engine rpm is above 2400 rpm, a 0
volt input will be seen by the PCM. A DTC will not
be entered into memory because the condition does
not occur within the specified rpm range.
A DTC indicates that the powertrain control mod-
ule (PCM) has recognized an abnormal signal in a
circuit or the system. A DTC may indicate the result
of a failure, but never identify the failed component
directly.
There are several operating conditions that the
PCM does not monitor and set a DTC for. Refer to
the following Monitored Circuits and Non-Monitored
Circuits in this section.
MONITORED CIRCUITS
The powertrain control module (PCM) can detect
certain problems in the fuel injection system.
Open or Shorted Circuit- The PCM can deter-
mine if sensor output (which is the input to PCM) is
within proper range. It also determines if the circuit
is open or shorted.
Output Device Current Flow- The PCM senses
whether the output devices are hooked up.
If there is a problem with the circuit, the PCM
senses whether the circuit is open, shorted to ground
(-), or shorted to (+) voltage.
Oxygen Sensor- The PCM can determine if the
oxygen sensor is switching between rich and lean.
This is, once the system has entered Closed Loop. Re-
fer to Open Loop/Closed Loop Modes Of Operation in
the Component Description/System Operation section
for an explanation of Closed (or Open) Loop opera-
tion.
NON-MONITORED CIRCUITS
The PCM does not monitor the following circuits,
systems or conditions that could have malfunctions
that result in driveability problems. A Diagnostic
Trouble Code (DTC) may not be displayed for these
conditions.
Fuel Pressure:Fuel pressure is controlled by the
vacuum assisted fuel pressure regulator. The PCM
cannot detect a clogged fuel pump inlet filter, clogged
in-line fuel filter, or a pinched fuel supply or return
Fig. 44 Fuel Injector Internal ComponentsÐTypical
JFUEL SYSTEM GENERAL DIAGNOSIS 14 - 51

line. However, these could result in a rich or lean
condition causing an oxygen sensor DTC to be stored
in the PCM.
Secondary Ignition Circuit:The PCM cannot
detect an inoperative ignition coil, fouled or worn
spark plugs, ignition cross firing, or open circuited
spark plug cables.
Engine Timing:The PCM cannot detect an incor-
rectly indexed timing chain, camshaft sprocket or
crankshaft sprocket. The PCM also cannot detect an
incorrectly indexed distributor. However, these could
result in a rich or lean condition causing an oxygen
sensor DTC to be stored in the PCM.
Cylinder Compression:The PCM cannot detect
uneven, low, or high engine cylinder compression.
Exhaust System:The PCM cannot detect a
plugged, restricted or leaking exhaust system.
Fuel Injector Malfunctions:The PCM cannot de-
termine if the fuel injector is clogged, or the wrong
injector is installed. However, these could result in a
rich or lean condition causing an oxygen sensor DTC
to be stored in the PCM.
Excessive Oil Consumption:Although the PCM
monitors exhaust stream oxygen content through ox-
ygen sensor (closed loop), it cannot determine exces-
sive oil consumption.
Throttle Body Air Flow:The PCM cannot detect
a clogged or restricted air cleaner inlet or air cleaner
element.
Evaporative System:The PCM will not detect a
restricted, plugged or loaded EVAP canister.
Vacuum Assist:Leaks or restrictions in the vac-
uum circuits of vacuum assisted engine control sys-
tem devices are not monitored by the PCM. However,
a vacuum leak at the MAP sensor will be monitored
and a diagnostic trouble code (DTC) will be gener-
ated by the PCM.
Powertrain Control Module (PCM) System
Ground:The PCM cannot determine a poor system
ground. However, a DTC may be generated as a re-
sult of this condition.
Powertrain Control Module (PCM) Connector
Engagement:The PCM cannot determine spread or
damaged connector pins. However, a DTC may be
generated as a result of this condition.
HIGH AND LOW LIMITS
The powertrain control module (PCM) compares in-
put signal voltages from each input device. It will es-
tablish high and low limits that are programmed into
it for that device. If the input voltage is not within
specifications and other Diagnostic Trouble Code
(DTC) criteria are met, a DTC will be stored in mem-
ory. Other DTC criteria might include engine rpm
limits or input voltages from other sensors or
switches. The other inputs might have to be sensed
by the PCM when it senses a high or low input volt-
age from the control system device in question.
ACCESSING DIAGNOSTIC TROUBLE CODES
A stored diagnostic trouble code (DTC) can be dis-
played by cycling the ignition key On-Off-On-Off-On
within three seconds and observing the malfunction
indicator lamp. This lamp is displayed on the instru-
ment panel as the CHECK ENGINE lamp (Figs. 45
or 46).
They can also be displayed through the use of the
Diagnostic Readout Box (DRB) scan tool. The DRB
scan tool connects to the data link connector in the
engine compartment (Figs. 47 or 48). For operation of
the DRB, refer to the appropriate Powertrain Diag-
nostic Procedures service manual.
Fig. 45 Check Engine LampÐXJ ModelsÐTypical
Fig. 46 Check Engine LampÐYJ ModelsÐTypical
JFUEL SYSTEM GENERAL DIAGNOSIS 14 - 53

clutch is slipping. Similarly, if slippage occurs in any
two forward gears, the rear clutch is slipping.
Applying the same method of analysis, note that
both clutches are applied in D range third gear only.
If the transmission slips in third gear, either the
front clutch or the rear clutch is slipping. By select-
ing another gear which does not use one of these
units, the slipping clutch can be determined.
Although road test analysis will help determine the
slipping unit, the actual cause of a malfunction may
not be determined until hydraulic and air pressure
tests are performed. Practically any condition can be
caused by leaking hydraulic circuits or sticking
valves. Unless the problem is an obvious one, do not
remove and disassemble the transmission until hy-
draulic and air pressure tests have been performed.
HYDRAULIC PRESSURE TEST
Hydraulic test pressures range from a low of one
psi (6.895 kPa) governor pressure, to 300 psi (2068.5
kPa) at the rear servo pressure port in reverse.
Use 100 psi Pressure Gauge C-3292 to check pres-
sure at the accumulator, front servo, governor and
fluid cooler line. Use 300 psi Gauge C-3293 to check
pressure at the rear servo. The 300 psi gauge can be
used at any other port when more than one gauge is
required for testing.
PRESSURE TEST PORT LOCATIONS
There are pressure test ports at the accumulator,
front servo, rear servo and governor.
Line pressure is checked at the accumulator port
on the right side of the case (Fig. 4). The front servo
release pressure port is at the right side of the case
just behind the filler tube opening (Fig. 4).
The rear servo pressure port is at the right rear of
the transmission case (Fig. 5).
On4x2models, the governor pressure port is at
the left side of case at the transmission rear (Fig. 5).
On4x4transmissions, the test port is in the driver
side of the adapter housing (Fig. 6).
PRESSURE TEST PROCEDURE
Connect a tachometer to the engine. Position the
tachometer so it can be observed from under the ve-
hicle. Raise the vehicle on a hoist that will allow the
wheels to rotate freely.
Test One-Transmission In 1 Range
This test checks pump output, pressure regu-
lation, and condition of the rear clutch and
rear servo circuits. Use both test gauges for
this test
(1) Connect Test Gauge C-3292 to line pressure
port and Test Gauge C-3293 to rear servo port (Figs.
4-6).
(2) Disconnect throttle and gearshift rods at trans-
mission.
(3) Start and run engine at 1000 rpm.
(4) Move valve body selector lever forward into 1
range.
(5) Read pressures on both gauges as transmission
throttle lever is moved from full forward to full rear-
ward position.
(a) Line pressure should be 54-60 psi (372-414
kPa) with throttle lever forward and gradually in-
crease to 90-96 psi (620-662 kPa) as lever is moved
rearward.
(b) Rear servo pressure should be same as line
pressure within 3 psi.
Fig. 4 Front Servo And Line Pressure Test Ports
Fig. 5 Rear Servo And Governor Pressure Test
Ports (4x2Transmission)
Fig. 6 Governor Pressure Test Port (4 x 4
Transmission)
21 - 72 30RH/32RH TRANSMISSION DIAGNOSISJ

Test Two-Transmission In 2 Range
This test checks pump output and pressure
regulation. Use 100 psi Test Gauge C-3292 for
this test.
(1) Connect test gauge to line pressure port (Fig.
4).
(2) Start and run engine at 1000 rpm.
(3) Move valve body selector lever one detent rear-
ward from full forward position (this is 2 range).
(4) Move transmission throttle lever from full for-
ward to full rearward position and read pressure at
both gauges.
(5) Line pressure should be 54-60 psi (372-414
kPa) with throttle lever forward and gradually in-
crease to 90-96 psi (620-662 kPa) as lever is moved
rearward.
Test Three-Transmission In Third Gear
This test checks pressure regulation and con-
dition of the front and rear clutch circuits.
Both gauges are required for this test.
(1) Connect one test gauge to line pressure port
and other gauge to front servo pressure port (Fig. 4).
Either gauge can be used at either port.
(2) Start and run engine at 1600 rpm.
(3) Move selector lever two detents rearward from
full forward position. This is D range.
(4) Read pressures on both gauges as transmission
throttle lever is moved from full forward to full rear-
ward position.
(a) Line pressure in third gear, should be 54-60
psi (372-414 kPa) with throttle lever forward and
gradually increase as lever is moved rearward.
(b) Front servo pressure in third gear, should be
within 3 psi (21 kPa) of line pressure, up to down-
shift point.
Test Four-Transmission In Reverse
This test checks pump output, pressure regu-
lation and the front clutch and rear servo cir-
cuits. Use 300 psi Pressure Test Gauge C-3293
for this test.
(1) Connect pressure test gauge to rear servo port
(Fig. 5).
(2) Start and run engine at 1600 rpm for test.
(3) Move valve body selector lever four detents
rearward from full forward position. This is Reverse
range.
(4) Move throttle lever all way forward then all the
way rearward and note gauge readings.
(5) Pressure should be 145 - 175 psi (1000-1207
kPa) with lever forward and increase to 230 - 280 psi
(1586-1931 kPa) as lever is moved rearward.
Test Five-Governor Pressure
This test checks governor operation by mea-
suring governor pressure response to changesin engine speed. It is usually not necessary to
check governor operation unless shift speeds
are incorrect or if the transmission will not
shift up or down. Use 100 psi Pressure Test
Gauge C-3292 for this test.
(1) Connect test gauge to governor pressure port
(Figs. 5 and 6).
(2) Move selector lever to D range.
(3) Apply service brakes. Start and run engine at
curb idle speed and note pressure. At idle and with
wheels stopped, pressure should be zero to 1-1/2 psi
maximum. If pressure exceeds this figure, governor
valve or weights are sticking open.
(4) Slowly increase engine speed and observe
speedometer and pressure test gauge. Governor pres-
sure should increase in proportion to vehicle speed
(approximately 1 psi for every 1 mph shown on
speedometer).
(5) Governor pressure rise should be smooth and
drop back to 0 to 1-1/2 psi when throttle is closed
and wheels are stopped.
(6) Compare results of pressure tests with analysis
chart (Fig. 7).
Fig. 7 Pressure Test Analysis Chart
J30RH/32RH TRANSMISSION DIAGNOSIS 21 - 73

CONVERTER STALL TEST
Stall testing involves determining maximum engine
rpm obtainable at full throttle with the rear wheels
locked and the transmission in D range. This test
checks the holding ability of the converter overrun-
ning clutch and both of the transmission clutches.
When stall testing is completed, refer to the Stall
Speed Specifications chart and Stall Speed Diagnosis
guides.
WARNING: NEVER ALLOW ANYONE TO STAND IN
FRONT OF THE VEHICLE DURING A STALL TEST.
ALWAYS BLOCK THE FRONT WHEELS AND APPLY
THE SERVICE AND PARKING BRAKES DURING
THE TEST.
STALL TEST PROCEDURE
(1) Connect tachometer to engine.
(2) Check and adjust transmission fluid level.
(3) Start and run engine until transmission fluid
reaches normal operating temperature.
(4) Block front wheels.
(5) Fully apply service and parking brakes.
(6) Open throttle completely and record maximum
engine rpm registered on tachometer. It will take
from 3 to 10 seconds to reach maximum rpm. How-
ever, once maximum rpm has been achieved,do not
hold wide open throttle for more than 5 sec-
onds.
CAUTION: Stalling the converter causes a rapid in-
crease in fluid temperature. To avoid fluid overheat-
ing, hold wide open throttle for no more than 5
seconds after reaching peak rpm. In addition, if
more than one stall test is required, run the engine
at 1000 rpm with the transmission in Neutral for at
least 20 seconds to cool the fluid.
(7) Stall speeds should be in 1700-2150 rpm range.
CAUTION: If engine exceeds 2150 rpm, release ac-
celerator pedal immediately as transmission clutch
slippage is occurring.
(8) Shift transmission into Neutral. Run engine for
20-30 seconds at 1000 rpm to cool fluid. Then stop
engine, shift transmission into Park and release
brakes.
(9) Refer to Stall Test Diagnosis.
STALL TEST DIAGNOSIS
Stall Speed Too Low
Low stall speeds with a properly tuned engine in-
dicate a torque converter overrunning clutch prob-
lem. The condition should be confirmed by road
testing prior to converter replacement.The converter overrunning clutch is slipping when
stall speeds are 250 to 350 rpm below specified min-
imum.
A converter overrunning clutch failure will result
in sluggish acceleration in all speed ranges. It will
also require greater than normal throttle opening to
maintain cruising speeds.
Stall Speed Too High
If stall speed exceeds 2150 rpm, transmission
clutch slippage is occurring.
Stall Speed Normal But Acceleration Is Sluggish
If stall speeds are within specified range but abnor-
mal throttle opening is required for acceleration, or
to maintain cruise speeds, the converter overrunning
clutch is seized. The torque converter will have to be
replaced.
Converter Noise During Test
A whining noise caused by fluid flow is normal dur-
ing a stall test. However, loud metallic noises indi-
cate a damaged converter. To confirm that noise is
originating from the converter, operate the vehicle at
light throttle in Drive and Neutral on a hoist and lis-
ten for noise from the converter housing.
AIR PRESSURE TEST
Air pressure testing can be used to check clutch
and band operation with the transmission either in
the vehicle, or on the work bench as a final check af-
ter overhaul.
Air pressure testing requires that the oil pan and
valve body be removed from the transmission.
The servo and clutch apply passages are shown in
Figure 8.
Air Test Procedure
(1) Place one or two fingers on the clutch housing
and apply air pressure through front clutch apply
passage (Fig. 8). Piston movement can be felt and a
soft thud heard as the clutch applies.
(2) Place one or two fingers on the clutch housing
and apply air pressure through rear clutch apply
passage (Fig. 8). Piston movement can be felt and a
soft thud heard as the clutch applies.
(3) Apply air pressure to the front servo apply pas-
sage. The servo rod should extend and cause the
band to tighten around the drum. Spring tension
should release the servo when air pressure is re-
moved.
(4) Apply air pressure to the rear servo apply pas-
sage. The servo rod should extend and cause the
band to tighten around the drum. Spring tension
should release the servo when air pressure is re-
moved.
21 - 74 30RH/32RH TRANSMISSION DIAGNOSISJ

CONVERTER HOUSING LEAK DIAGNOSIS
Two items must be established when diagnosing
leaks from the converter housing area. First, it must
be verified that a leak condition actually exists. And
second, the true source of the leak must be deter-
mined.
Some suspected converter housing fluid leaks may
not be leaks at all. Residual fluid in the housing, or
excess fluid spilled during factory fill or refill after
repair can be mistaken for a leak. In addition, a rear
main seal leak can also be mistaken for a pump seal
leak if care is exercised.
Converter housing leaks have several potential
sources. Through careful observation, a leak source
can be identified before removing the transmission
for repair.
Pump seal leaks tend to move along the drive hub
and onto the rear of the converter. Pump O-ring or
pump body leaks follow the same path as a seal leak
(Fig. 9).
Pump vent or pump attaching bolt leaks are gener-
ally deposited on the inside of the converter housing
and not on the converter itself (Fig. 9).
Pump seal or gasket leaks usually travel down the
inside of the converter housing.
Front band lever pin plug leaks are generally de-
posited on the housing and not on the converter.
LEAK DIAGNOSIS PROCEDURE
(1) Raise the rear of the vehicle and allow accumu-
lated fluid to drain out of the converter housing.
(2) Check and adjust the transmission fluid level.
(3) Raise the vehicle. Remove the converter hous-
ing dust cover and wipe as much fluid as possible
from the converter housing.(4) Fabricate a test probe (Fig. 10). Then attach
the probe to the converter housing with one of the
dust shield bolts (Fig. 10).
(5) Have a helper run the engine at 2500 rpm
(with the transmission in Neutral) for two minutes;
then stop the engine.
(6) Inspect the test probe and converter housing. If
a leak is evident, note the color of the fluid. Trans-
mission fluid is red. Engine oil ranges in color from
brown to green, or to black when the oil is dirty.
(7) If the probe upper surface is dry, the converter
and seal are not at fault. A path of fluid across the
probe upper surface indicates a converter or seal
leak. Fluid leakingunderthe probe is coming from
the pump housing area (Fig. 11).
(8) Fluid leaking under the probe could be from
the: pump seal and/or bushing, pump vent, kickdown
lever shaft access plug, pump bolts, or porous spots
in the pump body or transmission case (Fig. 11).
(9) If porous spots in the transmission case or
pump body are the suspected leak source, pressurize
the transmission as described in Leak Testing With
Air Pressure.
Fig. 8 Air Pressure Test Passages
Fig. 9 Typical Converter Housing Leak Paths
Fig. 10 Leak Test Probe
J30RH/32RH TRANSMISSION DIAGNOSIS 21 - 75