this information to control solenoids on transmission valve body. TCM
controls transmission shifting and torque converter lock-up.
TCM contains a self-diagnostic system, which will store
Diagnostic Trouble Codes (DTC) if failure or problem exists in
electronic control system. DTC can be retrieved to determine problem
area. See SELF-DIAGNOSTIC SYSTEM. TCM is located under left side of
instrument panel, left of steering column. See Fig. 1.
TCM INPUT DEVICES
Brakelight Switch Signal
Brakelight switch delivers input signal to TCM, indicating
vehicle braking. Brakelight switch is located on brake pedal support.
Cruise Control Electronic Control Unit (ECU)
Cruise control ECU delivers an input signal to control
overdrive operation in accordance with vehicle speed when cruise
control is operating. When in overdrive with cruise control on, if
vehicle speed drops 2 MPH less than the set speed, overdrive is
released to prevent reduction in vehicle speed. Once vehicle speed is
more than the set speed, overdrive function is resumed. If coolant
temperature is low, transmission will not shift into overdrive. Cruise
control ECU is located below center A/C vent, behind temperature
control panel on Montero. On Montero Sport, cruise control ECU is
located behind driver's kick panel.
Engine Coolant Temperature Sensor (ECT) Signal
Engine coolant temperature sensor delivers input signal to
TCM, indicating engine coolant temperature. Coolant temperature sensor
is located on engine.
Input & Output Shaft Speed Sensors
Sensors are magnetic pick-ups that monitor input and output
shaft speeds. AC waveforms are input to TCM by sensors. Sensors are
located on front and rear side of transmission case.
OD Switch Signal
The OD switch provides an input signal to TCM to indicate
when overdrive is selected by operator. When OD switch is depressed to
ON position, transmission will shift into 4th gear when shift lever is
in "D" position, and OD OFF light on instrument panel will go off.
When OD switch is released to OFF position, transmission will shift
into 3rd gear, and OD OFF light on instrument panel will come on. The
OD switch is mounted on shift lever.
Oil Temperature Sensor Signal
Oil temperature sensor provides TCM with ATF temperature
values. TCM uses this information to control shift points for maximum
performance. If transmission oil temperature exceeds standard values,
instrument panel ATF - TEMP light will come on. Sensor is mounted to
cooler line at transmission.
Park/Neutral Position (PNP) Switch Signal
PNP switch delivers an input signal to TCM indicating shift
lever position. Switch is located on side of transmission.
Throttle Position (TP) Sensor Signal
TP sensor delivers closed throttle and variable throttle
position input signals to TCM. TP sensor is located on side of
throttle body.
4WD Low Range Detection Switch
4WD low range detection switch provides information to TCM
If DTC 51 is set also, go to DTC 51: 1ST GEAR RATIO SIGNAL
INCORRECT test. If DTC 51 is not set, check overdrive brake for a
mechanical failure. See OVERDRIVE BRAKE in MITSUBISHI R4AW3 & V4AW3
OVERHAUL article.
SYMPTOM TROUBLE SHOOTING
NOTE: Check system using appropriate scan tool. See WIRING DIAGRAMS
for electrical schematics and COMPONENT TESTING.
COMMUNICATION WITH SCAN TOOL NOT POSSIBLE
If scan tool cannot communicate with TCM, check proper
connection with DLC. Check TCM power circuits, TCM ground circuits and
malfunctioning TCM.
SHIFT POINTS INCORRECT
If shift points are incorrect, check for DTCs. If no DTC is
present, check oil temperature sensor, pattern select switch, 4WD low
range detection switch and TCM for proper operation.
UPSHIFTS OCCUR SPONTANEOUSLY
If upshifting occurs spontaneously, check park/neutral
position switch, overdrive switch and TCM for proper operation.
TCC LOCK-UP MALFUNCTIONING
If TCC lock-up system is not operating properly, check torque
converter, valve body, lock-up switch and oil temperature switch.
COMPONENT TESTING
A/T FLUID TEMPERATURE SWITCH
1) Remove fluid temperature switch, located to rear of
neutral safety switch. Immerse switch in container of ATF up to top
threaded portion of switch. Using a DVOM, check continuity between
switch terminals. Continuity should not exist when fluid temperature
is 257
F (125C) or less.
2) When fluid is heated to 289-304F (143-151C), continuity
should exist. Replace switch if necessary. Apply thread sealant to
fluid temperature switch threads and install in transmission.
BRAKELIGHT SWITCH
1) Disconnect electrical connector from brakelight switch,
located near brake pedal. Using ohmmeter, ensure continuity exists
between terminal No. 2 (White/Red wire) and terminal No. 3 (Green
wire) with brake pedal released. Replace brakelight switch if
continuity does not exist. Continuity should not exist between
terminals No. 2 and No. 3 with brake pedal depressed.
2) If continuity does not exist, ensure brake pedal is
properly adjusted so brakelight switch has proper travel for switch
operation. If proper brakelight switch travel exists, replace
brakelight switch.
ENGINE COOLANT TEMPERATURE (ECT) SENSOR