2001 DODGE RAM change time

(1) Install sensor to intake manifold. Tighten to
12±15 N´m (110±130 in. lbs.) torque.
(2) Install electrical connector.
(3) Install air cleaner.
INSTALLATION - 8.0L
The intake manifold air temperature sensor is
located in the side of the intake manifold near the
front of throttle body (Fig. 35).
(1) Install sensor to intake manifold. Tighten to
12±15 N´m (110±130 in. lbs.) torque.
(2) Install electrical connector.
MANIFOLD ABSOLUTE
PRESSURE SENSOR
DESCRIPTION - 3.9L/5.2L/5.9L/8.0L
On 3.9L/5.2L/5.9L engines, the MAP sensor is
mounted on the side of the engine throttle body. The
sensor is connected to the throttle body with a rubber
L-shaped fitting.
On the 8.0L 10±cylinder engine, the MAP sensor is
mounted into the right side of the intake manifold.
OPERATION - 3.9L/5.2L/5.9L/8.0L
The MAP sensor is used as an input to the Power-
train Control Module (PCM). It contains a silicon
based sensing unit to provide data on the manifold
vacuum that draws the air/fuel mixture into the com-
bustion chamber. The PCM requires this information
to determine injector pulse width and spark advance.
When manifold absolute pressure (MAP) equals
Barometric pressure, the pulse width will be at max-
imum.
A 5 volt reference is supplied from the PCM and
returns a voltage signal to the PCM that reflects
manifold pressure. The zero pressure reading is 0.5V
and full scale is 4.5V. For a pressure swing of 0±15
psi, the voltage changes 4.0V. To operate the sensor,
it is supplied a regulated 4.8 to 5.1 volts. Ground is
provided through the low-noise, sensor return circuit
at the PCM.
The MAP sensor input is the number one contrib-
utor to fuel injector pulse width. The most important
function of the MAP sensor is to determine baromet-
ric pressure. The PCM needs to know if the vehicle is
at sea level or at a higher altitude, because the air
density changes with altitude. It will also help to cor-
rect for varying barometric pressure. Barometric
pressure and altitude have a direct inverse correla-
tion; as altitude goes up, barometric goes down. At
key-on, the PCM powers up and looks at MAP volt-
age, and based upon the voltage it sees, it knows the
current barometric pressure (relative to altitude).
Once the engine starts, the PCM looks at the voltageagain, continuously every 12 milliseconds, and com-
pares the current voltage to what it was at key-on.
The difference between current voltage and what it
was at key-on, is manifold vacuum.
During key-on (engine not running) the sensor
reads (updates) barometric pressure. A normal range
can be obtained by monitoring a known good sensor.
As the altitude increases, the air becomes thinner
(less oxygen). If a vehicle is started and driven to a
very different altitude than where it was at key-on,
the barometric pressure needs to be updated. Any
time the PCM sees Wide Open Throttle (WOT), based
upon Throttle Position Sensor (TPS) angle and RPM,
it will update barometric pressure in the MAP mem-
ory cell. With periodic updates, the PCM can make
its calculations more effectively.
The PCM uses the MAP sensor input to aid in cal-
culating the following:
²Manifold pressure
²Barometric pressure
²Engine load
²Injector pulse-width
²Spark-advance programs
²Shift-point strategies (certain automatic trans-
missions only)
²Idle speed
²Decel fuel shutoff
The MAP sensor signal is provided from a single
piezoresistive element located in the center of a dia-
phragm. The element and diaphragm are both made
of silicone. As manifold pressure changes, the dia-
phragm moves causing the element to deflect, which
stresses the silicone. When silicone is exposed to
stress, its resistance changes. As manifold vacuum
increases, the MAP sensor input voltage decreases
proportionally. The sensor also contains electronics
that condition the signal and provide temperature
compensation.
The PCM recognizes a decrease in manifold pres-
sure by monitoring a decrease in voltage from the
reading stored in the barometric pressure memory
cell. The MAP sensor is a linear sensor; meaning as
pressure changes, voltage changes proportionately.
The range of voltage output from the sensor is usu-
ally between 4.6 volts at sea level to as low as 0.3
volts at 26 in. of Hg. Barometric pressure is the pres-
sure exerted by the atmosphere upon an object. At
sea level on a standard day, no storm, barometric
pressure is approximately 29.92 in Hg. For every 100
feet of altitude, barometric pressure drops .10 in. Hg.
If a storm goes through it can change barometric
pressure from what should be present for that alti-
tude. You should know what the average pressure
and corresponding barometric pressure is for your
area.
14 - 44 FUEL INJECTION - GASOLINEBR/BE
INTAKE AIR TEMPERATURE SENSOR (Continued)

(3) Install MAP sensor mounting bolts (screws).
Tighten screws to 3 N´m (25 in. lbs.) torque.
(4) Install air cleaner.
INSTALLATION - 8.0L
The MAP sensor is mounted into the right upper
side of the intake manifold (Fig. 38). A rubber gasket
is used to seal the sensor to the intake manifold. The
rubber gasket is part of the sensor and is not ser-
viced separately.
(1) Check the condition of the sensor seal. Clean
the sensor and lubricate the rubber gasket with clean
engine oil.
(2) Clean the sensor opening in the intake mani-
fold.
(3) Install the sensor into the intake manifold.
(4) Install sensor mounting bolts. Tighten bolts to
2 N´m (20 in. lbs.) torque.
(5) Install the electrical connector to sensor.
O2 SENSOR
DESCRIPTION
The Oxygen Sensors (O2S) are attached to, and
protrude into the vehicle exhaust system. Depending
on the emission package, the vehicle may use a total
of either 2 or 4 sensors.
3.9L/5.2L/Light Duty 5.9L Engine:Four sensors
are used: 2 upstream (referred to as 1/1 and 2/1) and
2 downstream (referred to as 1/2 and 2/2). With this
emission package, the right upstream sensor (2/1) is
located in the right exhaust downpipe just before the
mini-catalytic convertor. The left upstream sensor
(1/1) is located in the left exhaust downpipe just
before the mini-catalytic convertor. The right down-
stream sensor (2/2) is located in the right exhaust
downpipe just after the mini-catalytic convertor, and
before the main catalytic convertor. The left down-
stream sensor (1/2) is located in the left exhaust
downpipe just after the mini-catalytic convertor, and
before the main catalytic convertor.
Medium and Heavy Duty 8.0L V-10 Engine:
Four sensors are used (2 upstream, 1 pre-catalyst
and 1 post-catalyst). With this emission package, the
1/1 upstream sensor (left side) is located in the left
exhaust downpipe before both the pre-catalyst sensor
(1/2), and the main catalytic convertor. The 2/1
upstream sensor (right side) is located in the right
exhaust downpipe before both the pre-catalyst sensor
(1/2), and the main catalytic convertor. The pre-cata-
lyst sensor (1/2) is located after the 1/1 and 2/1 sen-
sors, and just before the main catalytic convertor.
The post-catalyst sensor (1/3) is located just after the
main catalytic convertor.Heavy Duty 5.9L Engine:Two sensors are used.
They arebothreferred to as upstream sensors (left
side is referred to as 1/1 and right side is referred to
as 2/1). With this emission package, a sensor is
located in each of the exhaust downpipes before the
main catalytic convertor.
OPERATION
An O2 sensor is a galvanic battery that provides
the PCM with a voltage signal (0-1 volt) inversely
proportional to the amount of oxygen in the exhaust.
In other words, if the oxygen content is low, the volt-
age output is high; if the oxygen content is high the
output voltage is low. The PCM uses this information
to adjust injector pulse-width to achieve the
14.7±to±1 air/fuel ratio necessary for proper engine
operation and to control emissions.
The O2 sensor must have a source of oxygen from
outside of the exhaust stream for comparison. Cur-
rent O2 sensors receive their fresh oxygen (outside
air) supply through the wire harness. This is why it
is important to never solder an O2 sensor connector,
or pack the connector with grease.
Four wires (circuits) are used on each O2 sensor: a
12±volt feed circuit for the sensor heating element; a
ground circuit for the heater element; a low-noise
sensor return circuit to the PCM, and an input cir-
cuit from the sensor back to the PCM to detect sen-
sor operation.
Oxygen Sensor Heaters/Heater Relays:
Depending on the emissions package, the heating ele-
ments within the sensors will be supplied voltage
from either the ASD relay, or 2 separate oxygen sen-
sor relays. Refer to 8, Wiring Diagrams to determine
which relays are used.
The O2 sensor uses a Positive Thermal Co-efficient
(PTC) heater element. As temperature increases,
resistance increases. At ambient temperatures
around 70ÉF, the resistance of the heating element is
approximately 4.5 ohms. As the sensor's temperature
increases, resistance in the heater element increases.
This allows the heater to maintain the optimum
operating temperature of approximately 930É-1100ÉF
(500É-600É C). Although the sensors operate the
same, there are physical differences, due to the envi-
ronment that they operate in, that keep them from
being interchangeable.
Maintaining correct sensor temperature at all times
allows the system to enter into closed loop operation
sooner. Also, it allows the system to remain in closed
loop operation during periods of extended idle.
In Closed Loop operation, the PCM monitors cer-
tain O2 sensor input(s) along with other inputs, and
adjusts the injector pulse width accordingly. During
Open Loop operation, the PCM ignores the O2 sensor
input. The PCM adjusts injector pulse width based
14 - 46 FUEL INJECTION - GASOLINEBR/BE
MANIFOLD ABSOLUTE PRESSURE SENSOR (Continued)

(3) Install the remaining cable housing end into
and through the dash panel opening (snaps into posi-
tion). The two plastic pinch tabs (Fig. 21) should lock
the cable to dash panel.
(4) From inside the vehicle, hold up the accelera-
tor pedal. Install the throttle cable core wire and
plastic cable retainer into and through the upper end
of the pedal arm (the plastic retainer is snapped into
the pedal arm). When installing the plastic retainer
to the accelerator pedal arm, note the index tab on
the pedal arm (Fig. 21). Align the index slot on the
plastic cable retainer to this index tab.
THROTTLE POSITION SENSOR
DESCRIPTION
The 3±wire Throttle Position Sensor (TPS) is
mounted on the throttle body and is connected to the
throttle blade.
OPERATION
The TPS is a 3±wire variable resistor that provides
the Powertrain Control Module (PCM) with an input
signal (voltage) that represents the throttle blade
position of the throttle body. The sensor is connected
to the throttle blade shaft. As the position of the
throttle blade changes, the resistance (output volt-
age) of the TPS changes.The PCM supplies approximately 5 volts to the
TPS. The TPS output voltage (input signal to the
PCM) represents the throttle blade position. The
PCM receives an input signal voltage from the TPS.
This will vary in an approximate range of from .26
volts at minimum throttle opening (idle), to 4.49 volts
at wide open throttle. Along with inputs from other
sensors, the PCM uses the TPS input to determine
current engine operating conditions. In response to
engine operating conditions, the PCM will adjust fuel
injector pulse width and ignition timing.
The PCM needs to identify the actions and position
of the throttle blade at all times. This information is
needed to assist in performing the following calcula-
tions:
²Ignition timing advance
²Fuel injection pulse-width
²Idle (learned value or minimum TPS)
²Off-idle (0.06 volt)
²Wide Open Throttle (WOT) open loop (2.608
volts above learned idle voltage)
²Deceleration fuel lean out
²Fuel cutoff during cranking at WOT (2.608 volts
above learned idle voltage)
²A/C WOT cutoff (certain automatic transmis-
sions only)
REMOVAL - 3.9L/5.2L/5.9L
The TPS is located on the side of the throttle body.
(1) Remove air intake tube at throttle body.
(2) Disconnect TPS electrical connector.
(3) Remove two TPS mounting bolts (Fig. 47).
(4) Remove TPS from throttle body.
Fig. 46 Cable Release
1-TAB
Fig. 47 TPS Mounting BoltsÐ3.9L/5.2L/5.9L Engines
1 - THROTTLE POSITION SENSOR
2 - MOUNTING SCREWS
BR/BEFUEL INJECTION - GASOLINE 14 - 51
THROTTLE CONTROL CABLE (Continued)

Always cover or cap any open fuel connections before
a fuel system repair is performed.
Each fuel injector connector tube contains an edge
filter (Fig. 13) that breaks up small contaminants
that enter the injector. The edge filter uses the injec-
tors pulsating high-pressure to break up most parti-
cles so they are small enough to pass through the
injector.The edge filters are not a substitute for
proper cleaning and covering of all fuel system
components during repair.
The bottom of each fuel injector is sealed to the
cylinder head with a1.5mmthick copper shim (gas-
ket) (Fig. 12). The correct thickness shim must
always be re-installed after removing an injector.
Fuel pressure in the injector circuit decreases after
injection. The injector needle valve is immediately
closed by the needle valve spring and fuel flow into
the combustion chamber is stopped. Exhaust gases
are prevented from entering the injector nozzle by
the needle valve.
DIAGNOSIS AND TESTINGÐFUEL INJECTOR
TEST
The fuel injectors are located in the top of the cylin-
der head between the intake/exhaust valves (Fig. 14).
A leaking fuel injector can cause fuel knock, poor
performance, black smoke, poor fuel economy and
rough engine idle. If fuel injector needle valve does
not operate properly, engine may misfire and produce
low power.
A leak in injection pump-to-injector high-pressure
fuel line can cause many of same symptoms as mal-
functioning injector. Inspect for leaks in high-pressure
lines before checking for malfunctioning fuel injector.
WARNING: THE INJECTION PUMP SUPPLIES HIGH-
PRESSURE FUEL OF UP TO APPROXIMATELY
120,000 kPa (17,400 psi) TO EACH INDIVIDUAL
INJECTOR THROUGH HIGH-PRESSURE LINES. FUEL
UNDER THIS AMOUNT OF PRESSURE CAN PENE-
TRATE SKIN AND CAUSE PERSONAL INJURY. WEAR
SAFETY GOGGLES AND ADEQUATE PROTECTIVE
CLOTHING. AVOID CONTACT WITH FUEL SPRAY
WHEN BLEEDING HIGH-PRESSURE FUEL LINES.
WARNING: DO NOT BLEED AIR FROM FUEL SYS-
TEM OF A HOT ENGINE. DO NOT ALLOW FUEL TO
SPRAY ONTO EXHAUST MANIFOLD WHEN BLEED-
ING AIR FROM FUEL SYSTEM.
(1) To determine which fuel injector is malfunc-
tioning, run engine and isolate each cylinder using
DRB scan tool.The DRB scan tool lists the injec-
tor firing order in both cylinder numerical
order (1±2±3±4±5±6), and actual firing order
(1±5±3±6±2±4).
(2) Note RPM drop for each cylinder. As an alter-
native, loosen high-pressure fuel line fitting at fuel
injector connector tube (Fig. 15). Listen for a change
in engine speed. After testing, tighten line fitting to
40 N´m (30 ft. lbs.) torque. If engine speed drops,
injector was operating normally. If engine speed
remains same, injector may be malfunctioning. Test
all injectors in same manner one at a time.
Fig. 14 Fuel Injector Connections
1 - CONNECTOR
2 - O-RING
3 - FERRULE
4 - FITTING
5 - FUEL LINE
6 - INJECTOR
Fig. 15 Inspecting Injector Operation
1 - HIGH-PRESSURE FUEL LINE
BR/BEFUEL INJECTION - DIESEL 14 - 95
FUEL INJECTOR (Continued)

PUMP
TABLE OF CONTENTS
page page
PUMP
DESCRIPTION...........................31
OPERATION.............................31
DIAGNOSIS AND TESTING.................31
PUMP LEAKAGE.......................31
STANDARD PROCEDURE..................31
POWER STEERING PUMP - INITIAL
OPERATION...........................31
FLUSHING POWER STEERING SYSTEM.....32
REMOVAL..............................33
INSTALLATION...........................35SPECIAL TOOLS.........................36
PULLEY
REMOVAL..............................36
INSTALLATION...........................36
HOSES - PRESSURE
DESCRIPTION...........................37
OPERATION.............................37
HOSES - RETURN
DESCRIPTION...........................37
OPERATION.............................37
PUMP
DESCRIPTION
The P-Series pump is used on these vehicles (Fig.
1). The pump shaft has a pressed-on pulley that is
belt driven by the crankshaft pulley on gasoline
engines. The pump is driven off the back of the vac-
uum pump on the diesel engine.
Trailer tow option vehicles are equipped with a
power steering pump oil cooler. The oil cooler is
mounted to the front crossmember.
NOTE: Power steering pumps are not interchange-
able with pumps installed on other vehicles.
OPERATION
Hydraulic pressure is provided by the pump for the
power steering gear. The power steering pump is a
constant flow rate and displacement, vane-type
pump. The pump is connected to the steering gear
via the pressure hose and the return hose. On vehi-
cles equipped with a hydraulic booster, the pump
supplies the hydraulic pressure for the booster.
DIAGNOSIS AND TESTING - PUMP LEAKAGE
(1) Possible pump leakage areas. (Fig. 2).
STANDARD PROCEDURE - POWER STEERING
PUMP - INITIAL OPERATION
WARNING: THE FLUID LEVEL SHOULD BE
CHECKED WITH ENGINE OFF TO PREVENT INJURY
FROM MOVING COMPONENTS.
CAUTION: Use MOPAR Power Steering Fluid or
equivalent. Do not use automatic transmission fluid
and do not overfill.
Wipe filler cap clean, then check the fluid level.
The dipstick should indicateCOLDwhen the fluid is
at normal temperature.
(1) Turn steering wheel all the way to the left
(2) Fill the pump fluid reservoir to the proper level
and let the fluid settle for at least two (2) minutes.
(3) Raise the front wheels off the ground.
(4) Slowly turn the steering wheel lock-to-lock 20
times with the engine off while checking the fluid
level.
Fig. 1 P-SeriesÐPump
1 - RESERVOIR CAP AND DIPSTICK
2 - RESERVOIR
BR/BEPUMP 19 - 31

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-
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.
BR/BEAUTOMATIC TRANSMISSION - 42RE 21 - 195
ELECTRONIC GOVERNOR (Continued)

(15) Using a suitable gauge bar and dial indicator,
measure clutch pack clearance (Fig. 222).
(a) Position gauge bar across the clutch drum
with the dial indicator pointer on the pressure
plate (Fig. 222).
(b) Using two small screw drivers, lift the pres-
sure plate and release it.
(c) Zero the dial indicator.
(d) Lift the pressure plate until it contacts the
snap-ring and record the dial indicator reading.
Clearance should be 0.559 - 0.914 mm (0.022 -
0.036 in.). If clearance is incorrect, steel plates, discs,
selective snap ring and pressure plates may have to
be changed.
The selective snap-ring thicknesses are:
²0.107-0.109 in.
²0.098-0.100 in.
²0.095-0.097 in.
²0.083-0.085 in.
²0.076-0.078 in.
²0.071-0.073 in.
²0.060-0.062 in.
(16) Coat rear clutch thrust washer with petro-
leum jelly and install washer over input shaft and
into clutch retainer (Fig. 223). Use enough petroleum
jelly to hold washer in place.
REAR SERVO
DESCRIPTION
The rear (low/reverse) servo consists of a single
stage or diameter piston and a spring loaded plug.
The spring is used to cushion the application of the
rear (low/reverse) band.
OPERATION
While in the de-energized state (no pressure
applied), the piston is held up in its bore by the pis-
ton spring. The plug is held down in its bore, in the
piston, by the plug spring. When pressure is applied
to the top of the piston, the plug is forced down in its
bore, taking up any clearance. As the piston moves, it
causes the plug spring to compress, and the piston
moves down over the plug. The piston continues to
move down until it hits the shoulder of the plug and
fully applies the band. The period of time from the
initial application, until the piston is against theshoulder of the plug, represents a reduced shocking
of the band that cushions the shift.
Fig. 222 Checking Rear Clutch Pack Clearance
1 - DIAL INDICATOR
2 - PRESSURE PLATE
3 - SNAP-RING
4-STAND
5 - REAR CLUTCH
6 - GAUGE BAR
Fig. 223 Installing Rear Clutch Thrust Washer
1 - REAR CLUTCH RETAINER
2 - REAR CLUTCH THRUST WASHER
21 - 250 AUTOMATIC TRANSMISSION - 42REBR/BE
REAR CLUTCH (Continued)

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 absence
of 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-
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
21 - 366 AUTOMATIC TRANSMISSION - 44REBR/BE
ELECTRONIC GOVERNOR (Continued)