Villager V6-181 3.0L SOHC VIN 1 EFI (1997)
Control Module: Description and Operation
TRANSMISSION CONTROL MODULE
The Transmission Control Module (TCM) is separate from the Powertrain Control Module (PCM). Both control modules are used to determine the
operational characteristics of the transaxle, such as shift timing or lockup. These characteristics are calculated with a series of switch and sensor inputs
to produce optimum driveability.
SELF DIAGNOSIS FUNCTION
The TCM has a self diagnosis function which monitors the electrical circuits of certain sensors and solenoids. These are:
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Coasting clutch solenoid.
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Line pressure solenoid.
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Transmission (TR) switch.
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Shift solenoid A.
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Shift solenoid B.
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Throttle Position (TP) sensor.
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Torque converter clutch (TCC) solenoid.
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Vehicle Speed Sensor (VSS).
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Pulse Signal Generator (PSG) (Turbine Shaft Speed (TSS) sensor). This self diagnosis function is a function of the fail safe control system. When
one of these sensor or solenoid circuit readings is out of range, then the self diagnosis function places the 4F20E automatic transaxle in the fail
safe mode.
FAIL SAFE FUNCTION
The 4F20E automatic transaxle is equipped with a fail safe control system. If the vehicle sustains damage to one of the components listed below, the
fail safe function is activated. The fail safe action is controlled by the TCM. Fail safe operation can be detected by observing the OVERDRIVE (O/D)
OFF lamp. The O/D OFF lamp will blink for approximately eight seconds when the ignition switch is turned ON.
NOTE: Fail safe may be activated even if no electrical circuits are damaged. An example of this condition is excessive wheel spin. If this occurs
the vehicle will be placed in third gear and remain in third until the ignition switch is cycled. Once the ignition switch is cycled, the fail safe action
will be deactivated and the vehicle will return to its normal shift pattern.
COMPONENT MALFUNCTION vs. FAIL SAFE ACTION
Coasting clutch solenoid:
Stops the coasting clutch control. During deceleration there will always be engine braking.
Line pressure solenoid:
Line pressure is increased to maximum pressure.
TR switch:
Gearshift lever moves the manual valve and gear positions are selected manually.
Shift solenoids A and/or B:
When the D range or 2 range is selected, the vehicle will be in 3rd gear. If the 1 range is selected, the vehicle will be in 2nd gear. There are no
upshifts or downshifts.
TP sensor:
TCM uses idle switch and Wide Open Throttle (WOT) switch. When idle switch is closed, line pressure is reduced to minimum pressure. When
the idle switch is open, line pressure is increased to a maximum. The WOT switch is used to detect a 8/8 throttle opening.
Torque converter clutch (TCC) solenoid:
The transaxle will not enter lockup.
Vehicle speed sensor (VSS) or pulse signal generator (PSG):
If either of the sensors fail, the other sensor is used as the main signal. This does not affect drive ability.
