module DODGE RAM 1500 1998 2.G Workshop Manual

(11) Remove the shift cable from the column shift
lever actuator (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 32RH/GEAR SHIFT
CABLE - REMOVAL). (Fig. 3).
(12) Release the shift cable from the column
bracket and remove it from the bracket.
(13) Remove the SKIM module in order to discon-
nect the electrical connector.
(14) Remove the upper steering shaft coupler bolt
and slide the shaft down (Fig. 4) & (Fig. 5)(15) Remove the brake light switch and discard
(Refer to 8 - ELECTRICAL/LAMPS/LIGHTING -
EXTERIOR/BRAKE LAMP SWITCH - REMOVAL).
(16) Remove the four steering column mounting
nuts (Fig. 6).
Fig. 3 SHIFT CABLE CONNECTOR
1 - Shift lever
2 - Cable Connection
3 - Overdrive Electrical Wiring
4 - Mounting Screws
Fig. 4 COUPLER SHAFT
1 - MOUNTING HOLES
2 - COUPLER BOLT HOLE
Fig. 5 UPPER STEERING COUPLER
1 - STEERING COUPLER
2 - PINCH BOLT HOLE
Fig. 6 MOUNTING HOLES
1 - MOUNTING HOLES
19 - 8 COLUMNDR
COLUMN (Continued)

(17) Remove the steering column assembly from
the vehicle. (Fig. 7)
INSTALLATION
WARNING: BEFORE SERVICING THE STEERING
COLUMN THE AIRBAG SYSTEM MUST BE DIS-
ARMED. REFER TO ELECTRICAL RESTRAINT SYS-
TEM FOR SERVICE PROCEDURES. FAILURE TO DO
SO MAY RESULT IN ACCIDENTAL DEPLOYMENT OF
THE AIRBAG AND POSSIBLE PERSONAL INJURY.
CAUTION: All fasteners must be torqued to specifi-
cation to ensure proper operation of the steering
column.
(1) Position the steering column on the dash panel
support and loosely install the mounting nuts.
(2) Firmly slide the steering column upward
against the studs in dash panel and hand tighten the
nuts.
(3) Install the steering shaft coupler on the steer-
ing shaft and loosely install anewbolt.
(4) Center steering column in dash opening and
tighten mounting nuts to 28 N´m (250 in. lbs.).
NOTE: Torque the upper left nut first then the lower
right nut. Then torque the lower left nut then the
upper right nut.
NOTE: A new bolt must be used for reinstallation.
(5) Tighten the coupler bolt to 57 N´m (42 ft. lbs.).(6) Install a new brake light switch (Refer to 8 -
ELECTRICAL/LAMPS/LIGHTING - EXTERIOR/
BRAKE LAMP SWITCH - REMOVAL).
(7) Install the shifter cable. (Refer to 21 - TRANS-
MISSION/TRANSAXLE/AUTOMATIC - 32RH/GEAR
SHIFT CABLE - INSTALLATION)
(8) Connect the wiring harness to the column.
(9) Install the SKIM module.
(10) Install the clockspring(Refer to 8 - ELECTRI-
CAL/RESTRAINTS/CLOCKSPRING - REMOVAL).
(11) Install the shrouds.
(12) Install the steering column opening cover
(Refer to 23 - BODY/INSTRUMENT PANEL/STEER-
ING COLUMN OPENING COVER - INSTALLA-
TION).
(13) Align the spline on the wheel hub to shaft.
(14) Then install the steering wheel and install a
newbolt. Tighten the bolt to 61 N´m (45 ft. lbs.).
(15) Install the airbag (Refer to 8 - ELECTRICAL/
RESTRAINTS/DRIVER AIRBAG - INSTALLATION).
(16) Install the two steering wheel switches.
(17) Install the tilt lever handle.
(18) Install the negative battery terminal.
(19) Test the operation of the horn, Electronic
PRNDL Indicator, lights and any other functions that
are steering column operated.
IGNITION SWITCH
DESCRIPTION
The ignition switch is located on the steering col-
umn. It is used as the main on/off switching device
for most electrical components. The mechanical key
cylinder is used to engage/disengage the electrical
ignition switch.
OPERATION
Vehicles equipped with an automatic trans-
mission and a steering column mounted shifter:
an interlock device is located within the shift cable.
This interlock device is used to lock the transmission
shifter in the PARK position when the key cylinder is
in any position and the brake pedal is not depressed.
DIAGNOSIS AND TESTING - IGNITION SWITCH
TEST AND REPAIR
If the key removal effort is excessive on a vehicle
with a automatic transmission first adjust the shift
linkage, (Refer to 21 - TRANSMISSION/TRANS-
AXLE/AUTOMATIC - 46RE/GEAR SHIFT CABLE -
ADJUSTMENTS).
If the ignition switch effort is excessive remove the
ignition key cylinder from the steering column. (Refer
to 19 - STEERING/COLUMN/LOCK CYLINDER
Fig. 7 STEERING COLUMN
1 - Steering Wheel
2 - Key Cylinder
3 - Gear Shift Lever
4 - Steering Column
5 - Tilt Lever Cable
DRCOLUMN 19 - 9
COLUMN (Continued)

(8) For columns without tilt remove the bracket to
gain access to the ignition switch mounting screws.
(Fig. 10)
(9) Disconnect the electrical connector at rear of
ignition switch (Fig. 11).
(10) Remove ignition switch mounting screw.
(11) Using a small screwdriver, push on locking
tab and remove switch from steering column.
INSTALLATION
The ignition key must be in the key cylinder for
cylinder removal. The key cylinder must be removed
first before installing ignition switch.
(1) Before installing ignition switch, rotate the slot
in the switch to the ON position.(2) Connect the electrical connector to rear of the
ignition switch. Make sure that locking tabs are fully
seated into wiring connector.
(3) Position switch to column and install the
mounting screw. Tighten screw to 3 N´m (26 in. lbs.).
(4) Install the tilt lever bracket mounting screws.
Tighten screws to 4.5 N´m (40 in. lbs.).
(5) If the column is non-tilt install the bracket.
Tighten screws to 4.5 N´m (40 in. lbs.) (Fig. 10)
(6) Position the wire retainer into the tilt lever
bracket.
(7) Reconnect the lower clockspring connectors.
(8) Install the key cylinder.
(9) Install steering column upper and lower
shrouds.
(10) Enable the airbag system. (Refer to 8 - ELEC-
TRICAL/RESTRAINTS/DRIVER AIRBAG - INSTAL-
LATION).
KEY-IN IGNITION SWITCH
DESCRIPTION
The key-in ignition switch is integral to the igni-
tion switch, which is mounted on the left side of the
steering column. It closes a path to ground for the
Central Timer Module (CTM) when the ignition key
is inserted in the ignition key cylinder and the driver
door ajar switch is closed (driver door is open). The
key-in ignition switch opens the ground path when
the key is removed from the ignition key cylinder.
The ground path is also opened when the driver door
ajar switch is open (driver door is closed).
The key-in ignition switch cannot be repaired and,
if faulty or damaged, the entire ignition switch must
be replaced, (Refer to 19 - STEERING/COLUMN/IG-
NITION SWITCH - REMOVAL).
DIAGNOSIS AND TESTING - IGNITION SWITCH
AND KEY LOCK CYLINDER
ELECTRICAL DIAGNOSIS
For ignition switch electrical schematics, refer to
Ignition Switch in the appropriate section of Electri-
cal Wiring Diagrams.
MECHANICAL DIAGNOSIS (KEY DIFFICULT TO
ROTATE)
(Refer to 19 - STEERING/COLUMN/IGNITION
SWITCH - DIAGNOSIS AND TESTING).
Fig. 10 IGNITION SWITCH WITHOUT TILT
1 - Ignition Switch Mounting Screws
2 - Non-Tilt Mounitng Bracket Screws
Fig. 11 IGNITION SWITCH
1 - Ignition Switch
2 - Ignition Switch Mounting Screws
DRCOLUMN 19 - 11
IGNITION SWITCH (Continued)

(4) Remove the support and lower the vehicle.
(5) Reconnect the return hose at the reservoir.
(6) Refill the power steering system,(Refer to 19 -
STEERING/PUMP - STANDARD PROCEDURE).
POWER STEERING PRESSURE
SWITCH
DESCRIPTION
A pressure sensing switch is used in the power
steering system. It is mounted on the high-pressure
steering hose (Fig. 9). This switch will be used with
both 3.7L and 5.7L engines. There is no pressure
switch used for the 4.7L or the 5.9L pump.
OPERATION
The switch is used on the 3.7L V-6 & 5.7L V-8
engines.
The power steering pressure switch provides an
input to the Powertrain Control Module (PCM). This
input is provided during periods of high steering
pump load and low engine rpm; such as during park-
ing maneuvers. The PCM increases the idle speed
through the Idle Air Control (IAC) motor. This is
done to prevent the engine from stalling under the
increased load.
When steering pump pressure exceeds 3275 kPa  
690 kPa (475 psi   100 psi), the Normally Closed
(NC) switch will open and the PCM will increase the
engine idle speed. This will prevent the engine from
stalling.
When pump pressure drops to approximately 1379
kPa (200 psi), the switch circuit will re-close and
engine idle speed will return to its previous setting.
REMOVAL - 3.7L & 5.7L
The power steering pressure switch is installed in
the power steering high-pressure hose (Fig. 9).
(1) Disconnect electrical connector from power
steering pressure switch.(2) Place a small container or shop towel beneath
switch to collect any excess fluid.
(3) Remove switch. Use back-up wrench on power
steering line to prevent line bending.
INSTALLATION - 3.7L & 5.7L
This switch is used only with the 3.7L V±6 and the
5.7L V-8 engines.
(1) Install power steering switch into power steer-
ing line.
(2) Tighten to 8±11 N´m (70±100 in. lbs.) torque.
(3) Connect electrical connector to switch.
(4) Check power steering fluid and add as neces-
sary.
(5) Start engine and again check power steering
fluid. Add fluid if necessary.
Fig. 9 PRESSURE SWITCH
1 - POWER STEERING PULLEY
2 - POWER STEERING PUMP HOUSING
3 - POWER STEERING FLUID RESERVOIR
4 - RETURN HOSE
5 - HIGH PRESSURE HOSE WITH PRESSURE SWITCH
19 - 46 PUMPDR
HOSES - LINK/COIL (Continued)

IDENTIFICATION
Transmission identification numbers are stamped
on the left side of the case just above the oil pan gas-
ket surface (Fig. 2). Refer to this information when
ordering replacement parts.
GEAR RATIOS
The 48RE gear ratios are:
1st.................................2.45:1
2nd................................1.45:1
3rd................................1.00:1
4th.................................0.69:1
Rev.................................2.20:1
OPERATION
The application of each driving or holding compo-
nent is controlled by the valve body based upon the
manual lever position, throttle pressure, and gover-
nor pressure. The governor pressure is a variable
pressure input to the valve body and is one of the
signals that a shift is necessary. First through fourth
gear are obtained by selectively applying and releas-
ing the different clutches and bands. Engine power is
thereby routed to the various planetary gear assem-
blies which combine with the overrunning clutch
assemblies to generate the different gear ratios. The
torque converter clutch is hydraulically applied and
is released when fluid is vented from the hydraulic
circuit by the torque converter control (TCC) solenoid
on the valve body. The torque converter clutch is con-
trolled by the Powertrain Control Module (PCM). The
torque converter clutch engages in fourth gear, and
in third gear under various conditions, such as when
the O/D switch is OFF, when the vehicle is cruising
on a level surface after the vehicle has warmed up.
The torque converter clutch can also be engaged in
the MANUAL SECOND gear position if high trans-
mission temperatures are sensed by the PCM. The
torque converter clutch will disengage momentarily
when an increase in engine load is sensed by the
PCM, such as when the vehicle begins to go uphill or
the throttle pressure is increased. The torque con-
verter clutch feature increases fuel economy and
reduces the transmission fluid temperature.
Since the overdrive clutch is applied in fourth gear
only and the direct clutch is applied in all ranges
except fourth gear, the transmission operation for
park, neutral, and first through third gear will be
described first. Once these powerflows are described,
the third to fourth shift sequence will be described.
1 - TORQUE CONVERTER 10 - OVERDRIVE CLUTCH
2 - INPUT SHAFT 11 - DIRECT CLUTCH
3 - OIL PUMP 12 - PLANETARY GEAR
4 - FRONT BAND 13 - INTERMEDIATE SHAFT
5 - FRONT CLUTCH 14 - OVERDRIVE OVERRUNNING CLUTCH
6 - REAR CLUTCH 15 - DIRECT CLUTCH SPRING
7 - PLANETARIES 16 - OVERDRIVE PISTON RETAINER
8 - REAR BAND 17 - OIL PAN
9 - OVERRUNNING CLUTCH 18 - VALVE BODY
Fig. 2 Transmission Part Number And Serial
Number Location
1 - PART NUMBER
2 - BUILD DATE
3 - SERIAL NUMBER
21 - 134 AUTOMATIC TRANSMISSION - 48REDR
AUTOMATIC TRANSMISSION - 48RE (Continued)

DIRECT DRIVE POWERFLOW
The vehicle has accelerated and reached the shift
point for the 2-3 upshift into direct drive (Fig. 8).
When the shift takes place, the front band is
released, and the front clutch is applied. The rear
clutch stays applied as it has been in all the forward
gears. With the front clutch now applied, engine
torque is now on the front clutch retainer, which is
locked to the sun gear driving shell. This means that
the sun gear is now turning in engine rotation (clock-
wise) and at engine speed. The rear clutch is still
applied so engine torque is also still on the front
annulus gear. If two members of the same planetary
set are driven, direct drive results. Therefore, when
two members are rotating at the same speed and in
the same direction, it is the same as being locked up.
The rear planetary set is also locked up, given the
sun gear is still the input, and the rear annulus gear
must turn with the output shaft. Both gears are
turning in the same direction and at the same speed.
The front and rear planet pinions do not turn at all
in direct drive. The only rotation is the input from
the engine to the connected parts, which are acting
as one common unit, to the output shaft.
FOURTH GEAR POWERFLOW
Fourth gear overdrive range is electronically con-
trolled and hydraulically activated. Various sensor
inputs are supplied to the powertrain control module
to operate the overdrive solenoid on the valve body.
The solenoid contains a check ball that opens and
closes a vent port in the 3-4 shift valve feed passage.
The overdrive solenoid (and check ball) are not ener-
gized in first, second, third, or reverse gear. The vent
port remains open, diverting line pressure from the
2-3 shift valve away from the 3-4 shift valve. The
Tow/Haul control switch must be in the ON position
to transmit overdrive status to the PCM. A 3-4
upshift occurs only when the overdrive solenoid is
energized by the PCM. The PCM energizes the over-
drive solenoid during the 3-4 upshift. This causes the
solenoid check ball to close the vent port allowing
line pressure from the 2-3 shift valve to act directly
on the 3-4 upshift valve. Line pressure on the 3-4
shift valve overcomes valve spring pressure moving
the valve to the upshift position. This action exposes
the feed passages to the 3-4 timing valve, 3-4 quick
fill valve, 3-4 accumulator, and ultimately to the
overdrive piston. Line pressure through the timing
Fig. 8 Direct Drive Powerflow
1 - FRONT CLUTCH APPLIED 6 - INPUT SHAFT
2 - OVER-RUNNING CLUTCH FREE-WHEELING 7 - OVER-RUNNING CLUTCH FREE-WHEELING
3 - OUTPUT SHAFT 8 - REAR CLUTCH APPLIED
4 - REAR CLUTCH APPLIED 9 - FRONT CLUTCH APPLIED
5 - OUTPUT SHAFT 10 - INPUT SHAFT
DRAUTOMATIC TRANSMISSION - 48RE 21 - 139
AUTOMATIC TRANSMISSION - 48RE (Continued)

(3) Have helper start and run engine at 1600 rpm
for test.
(4)
Move transmission shift lever four detents rear-
ward from full forward position. This is Reverse range.
(5) Move transmission throttle lever fully forward
then fully rearward and note reading at Gauge
C-3293-SP.
(6) Pressure should be 145 - 175 psi (1000-1207
kPa) with throttle lever forward and increase to 230 -
280 psi (1586-1931 kPa) as lever is gradually moved
rearward.
Test Five - Governor Pressure
This test checks governor operation by measuring
governor pressure response to changes in vehicle
speed. It is usually not necessary to check governor
operation unless shift speeds are incorrect or if the
transmission will not downshift. The test should be
performed on the road or on a hoist that will allow
the rear wheels to rotate freely.
(1) Move 100 psi Test Gauge C-3292 to governor
pressure port.
(2) Move transmission shift lever two detents rear-
ward from full forward position. This is D range.
(3) Have helper start and run engine at curb idle
speed. Then firmly apply service brakes so wheels
will not rotate.
(4) Note governor pressure:
²
Governor pressure should be no more than 20.6
kPa (3 psi) at curb idle speed and wheels not rotating.
²If pressure exceeds 20.6 kPa (3 psi), a fault
exists in governor pressure control system.
(5) Release brakes, slowly increase engine speed,
and observe speedometer and pressure test gauge (do
not exceed 30 mph on speedometer). Governor pres-
sure should increase in proportion to vehicle speed.
Or approximately 6.89 kPa (1 psi) for every 1 mph.
(6) Governor pressure rise should be smooth and
drop back to no more than 20.6 kPa (3 psi), after
engine returns to curb idle and brakes are applied to
prevent wheels from rotating.
(7)
Compare results of pressure test with analysis
chart.
Test Six - Transmission In Overdrive Fourth Gear
This test checks line pressure at the overdrive
clutch in fourth gear range. Use 300 psi Test Gauge
C-3293-SP for this test. The test should be performed
on the road or on a chassis dyno.
(1)
Remove tachometer; it is not needed for this test.
(2) Move 300 psi Gauge to overdrive clutch pres-
sure test port. Then remove other gauge and reinstall
test port plug.
(3) Lower vehicle.
(4) Turn OD switch on.(5) Secure test gauge so it can be viewed from
drivers seat.
(6) Start engine and shift into D range.
(7) Increase vehicle speed gradually until 3-4 shift
occurs and note gauge pressure.
(8) Pressure should be 524-565 kPa (76-82 psi)
with closed throttle and increase to 690-896 kPa
(100-130 psi) at 1/2 to 3/4 throttle. Note that pres-
sure can increase to around 965 kPa (140 psi) at full
throttle.
(9) Return to shop or move vehicle off chassis
dyno.
PRESSURE TEST ANALYSIS CHART
TEST CONDITION INDICATION
Line pressure OK during
any one testPump and regulator
valve OK
Line pressure OK in R
but low in D, 2, 1Leakage in rear clutch
area (seal rings, clutch
seals)
Pressure low in D Fourth
Gear RangeOverdrive clutch piston
seal, or check ball
problem
Pressure OK in 1, 2 but
low in D3 and RLeakage in front clutch
area
Pressure OK in 2 but low
in R and 1Leakage in rear servo
Front servo pressure in 2 Leakage in servo; broken
servo ring or cracked
servo piston
Pressure low in all
positionsClogged filter, stuck
regulator valve, worn or
faulty pump, low oil level
Governor pressure too
high at idle speedGovernor pressure
solenoid valve system
fault. Refer to diagnostic
book.
Governor pressure low at
all mph figuresFaulty governor pressure
solenoid, transmission
control module, or
governor pressure
sensor
Lubrication pressure low
at all throttle positionsClogged fluid cooler or
lines, seal rings leaking,
worn pump bushings,
pump, clutch retainer, or
clogged filter.
Line pressure high Output shaft plugged,
sticky regulator valve
Line pressure low Sticky regulator valve,
clogged filter, worn pump
DRAUTOMATIC TRANSMISSION - 48RE 21 - 143
AUTOMATIC TRANSMISSION - 48RE (Continued)

BTSI FUNCTION CHECK
(1) Verify removal of ignition key allowed in PARK
position only.
(2) When the shift lever is in PARK, the ignition
key cylinder should rotate freely from off to lock.
When the shifter is in any other position, the ignition
key should not rotate from off to lock.
(3) Shifting out of PARK should be possible when
the ignition key cylinder is in the off position.
(4) Shifting out of PARK should not be possible
while applying normal force, and ignition key cylin-
der is in the run or start positions, unless the foot
brake pedal is depressed approximately 1/2 inch
(12mm).
(5) Shifting out of PARK should not be possible
when the ignition key cylinder is in the accessory or
lock position.
(6) Shifting between any gear and NEUTRAL, or
PARK, may be done without depressing foot brake
with ignition switch in run or start positions.
(7) Engine starts must be possible with shifter
lever in PARK or NEUTRAL positions only. Engine
starts must not be possible in any position other than
PARK or NEUTRAL.
(8) With shifter lever in the:
²PARK position - Apply upward force on the shift
arm and remove pressure. Engine starts must be
possible.²PARK position - Apply downward force on the
shift arm and remove pressure. Engine starts must
be possible.
²NEUTRAL position - Normal position. Engine
starts must be possible.
²NEUTRAL position - Engine running and brakes
applied, apply upward force on the shift arm. Trans-
mission shall not be able to shift from neutral to
reverse.
ELECTRONIC GOVERNOR
DESCRIPTION
Governor pressure is controlled electronically. Com-
ponents used for governor pressure control include:
²Governor body
²Valve body transfer plate
²Governor pressure solenoid valve
²Governor pressure sensor
²Fluid temperature thermistor
²Throttle position sensor (TPS)
²Transmission speed sensor
²Powertrain control module (PCM)
GOVERNOR PRESSURE SOLENOID VALVE
The solenoid valve is a duty-cycle solenoid which
regulates the governor pressure needed for upshifts
and downshifts. It is an electro-hydraulic device
located in the governor body on the valve body trans-
fer plate (Fig. 76).
Fig. 75 Brake Transmission Interlock Mechanism
1 - STEERING COLUMN
2 - GEARSHIFT CABLE
3 - GEARSHIFT CABLE LOCK TAB
4 - BTSI SOLENOID LOCK TAB
5 - BTSI CONNECTOR
Fig. 76 Governor Pressure Solenoid Valve
1 - SOLENOID FILTER
2 - GOVERNOR PRESSURE SOLENOID
DRAUTOMATIC TRANSMISSION - 48RE 21 - 197
BRAKE TRANSMISSION SHIFT INTERLOCK SYSTEM (Continued)

GOVERNOR PRESSURE SENSOR
The governor pressure sensor measures output
pressure of the governor pressure solenoid valve (Fig.
77).
GOVERNOR BODY AND TRANSFER PLATE
The transfer plate is designed to supply transmis-
sion line pressure to the governor pressure solenoid
valve and to return governor pressure.
The governor pressure solenoid valve is mounted in
the governor body. The body is bolted to the lower
side of the transfer plate (Fig. 77).
GOVERNOR PRESSURE CURVES
There are four governor pressure curves pro-
grammed into the transmission control module. The
different curves allow the control module to adjust
governor pressure for varying conditions. One curve
is used for operation when fluid temperature is at, or
below, ±1ÉC (30ÉF). A second curve is used when fluid
temperature is at, or above, 10ÉC (50ÉF) during nor-
mal city or highway driving. A third curve is used
during wide-open throttle operation. The fourth curve
is used when driving with the transfer case in low
range.
OPERATION
Compensation is required for performance varia-
tions of two of the input devices. Though the slope of
the transfer functions is tightly controlled, offset may
vary due to various environmental factors or manu-
facturing tolerances.
The pressure transducer is affected by barometric
pressure as well as temperature. Calibration of the
zero pressure offset is required to compensate for
shifting output due to these factors.
Normal calibration will be performed when sump
temperature is above 50 degrees F, or in the absenceof sump temperature data, after the first 10 minutes
of vehicle operation. Calibration of the pressure
transducer offset occurs each time the output shaft
speed falls below 200 RPM. Calibration shall be
repeated each 3 seconds the output shaft speed is
below 200 RPM. A 0.5 second pulse of 95% duty cycle
is applied to the governor pressure solenoid valve
and the transducer output is read during this pulse.
Averaging of the transducer signal is necessary to
reject electrical noise.
Under cold conditions (below 50 degrees F sump),
the governor pressure solenoid valve response may
be too slow to guarantee 0 psi during the 0.5 second
calibration pulse. Calibration pulses are continued
during this period, however the transducer output
valves are discarded. Transducer offset must be read
at key-on, under conditions which promote a stable
reading. This value is retained and becomes the off-
set during the9cold9period of operation.
GOVERNOR PRESSURE SOLENOID VALVE
The inlet side of the solenoid valve is exposed to
normal transmission line pressure. The outlet side of
the valve leads to the valve body governor circuit.
The solenoid valve regulates line pressure to pro-
duce governor pressure. The average current sup-
plied to the solenoid controls governor pressure. One
amp current produces zero kPa/psi governor pres-
sure. Zero amps sets the maximum governor pres-
sure.
The powertrain control module (PCM) turns on the
trans control relay which supplies electrical power to
the solenoid valve. Operating voltage is 12 volts
(DC). The PCM controls the ground side of the sole-
noid using the governor pressure solenoid control cir-
cuit.
GOVERNOR PRESSURE SENSOR
The sensor output signal provides the necessary
feedback to the PCM. This feedback is needed to ade-
quately control governor pressure.
GOVERNOR BODY AND TRANSFER PLATE
The transfer plate channels line pressure to the
solenoid valve through the governor body. It also
channels governor pressure from the solenoid valve
to the governor circuit. It is the solenoid valve that
develops the necessary governor pressure.
GOVERNOR PRESSURE CURVES
LOW TRANSMISSION FLUID TEMPERATURE
When the transmission fluid is cold the conven-
tional governor can delay shifts, resulting in higher
than normal shift speeds and harsh shifts. The elec-
tronically controlled low temperature governor pres-
Fig. 77 Governor Pressure Sensor
1 - GOVERNOR BODY
2 - GOVERNOR PRESSURE SENSOR/TRANSMISSION FLUID
TEMPERATURE THERMISTOR
21 - 198 AUTOMATIC TRANSMISSION - 48REDR
ELECTRONIC GOVERNOR (Continued)

sure curve is higher than normal to make the
transmission shift at normal speeds and sooner. The
PCM uses a temperature sensor in the transmission
oil sump to determine when low temperature gover-
nor pressure is needed.
NORMAL OPERATION
Normal operation is refined through the increased
computing power of the PCM and through access to
data on engine operating conditions provided by the
PCM that were not available with the previous
stand-alone electronic module. This facilitated the
development of a load adaptive shift strategy - the
ability to alter the shift schedule in response to vehi-
cle load condition. One manifestation of this capabil-
ity is grade9hunting9prevention - the ability of the
transmission logic to delay an upshift on a grade if
the engine does not have sufficient power to main-
tain speed in the higher gear. The 3-2 downshift and
the potential for hunting between gears occurs with a
heavily loaded vehicle or on steep grades. When
hunting occurs, it is very objectionable because shifts
are frequent and accompanied by large changes in
noise and acceleration.
WIDE OPEN THROTTLE OPERATION
In wide-open throttle (WOT) mode, adaptive mem-
ory in the PCM assures that up-shifts occur at the
preprogrammed optimum speed. WOT operation is
determined from the throttle position sensor, which
is also a part of the emission control system. The ini-
tial setting for the WOT upshift is below the opti-
mum engine speed. As WOT shifts are repeated, the
PCM learns the time required to complete the shifts
by comparing the engine speed when the shifts occur
to the optimum speed. After each shift, the PCM
adjusts the shift point until the optimum speed is
reached. The PCM also considers vehicle loading,
grade and engine performance changes due to high
altitude in determining when to make WOT shifts. It
does this by measuring vehicle and engine accelera-
tion and then factoring in the shift time.
TRANSFER CASE LOW RANGE OPERATION
On four-wheel drive vehicles operating in low
range, the engine can accelerate to its peak more
rapidly than in Normal range, resulting in delayed
shifts and undesirable engine9flare.9The low range
governor pressure curve is also higher than normal
to initiate upshifts sooner. The PCM compares elec-
tronic vehicle speed signal used by the speedometer
to the transmission output shaft speed signal to
determine when the transfer case is in low range.REMOVAL
(1) Hoist and support vehicle on safety stands.
(2) Remove transmission fluid pan and filter.
(3) Disengage wire connectors from pressure sen-
sor and solenoid (Fig. 78).
(4) Remove screws holding pressure solenoid
retainer to governor body.
(5) Separate solenoid retainer from governor (Fig.
79).
Fig. 78 Governor Solenoid And Pressure Sensor
1 - PRESSURE SENSOR
2 - PRESSURE SOLENOID
3 - GOVERNOR
Fig. 79 Pressure Solenoid Retainer
1 - PRESSURE SOLENOID RETAINER
2 - GOVERNOR
DRAUTOMATIC TRANSMISSION - 48RE 21 - 199
ELECTRONIC GOVERNOR (Continued)