PCM Inputs

PCM Wiring Diagram:

PCM and Transmission Control Wiring

Wiring Diagram.:

PRNDL Switch Wiring



THROTTLE POSITION SENSOR
^ Measures the throttle position and inputs it into the PCM.
^ Provides data to develop the shift pattern.
^ There are two diagnostic codes associated with the sensor.
- Code 21 throttle position sensor too high.
- Code 22 throttle position sensor too low.
- Code 55 throttle position sensor out of adjustment.
- Code 70 intermittent throttle position.
The Fail-safe actions for codes 21 and 22 are:
^ Off mode of the Viscous Converter Clutch (VCC).
^ Inhibit 4th gear.
^ Use default value for TPS in second and third gear, may disable third gear.
The Fail-safe action for code 55 is:
^ Use default value for TPS.
It will recover upon a valid range.


VEHICLE SPEED SENSOR
^ Measures the speed of the final drive assembly.
^ Provides data to develop the shift pattern.
^ Generates a voltage waveform and its frequency. Determines vehicle speed.
^ There are two diagnostic codes associated with the sensor:
- Code 24 vehicle speed sensor.
^ Detects when the signal is too low.
- Code 75 intermittent speed sensor.
^ Detects a large drop in frequency.
The Fail-safe actions for code 24 are:
^ VCC will not operate for the ignition cycle.
^ Third and fourth gears will be disabled under most conditions. It will recover when vehicle speed is above a specific value.


ENGINE COOLANT TEMPERATURE.
^ Measures the engine coolant temperature.
^ The PCM will not command the VCC until the engine coolant temperature is above a specific temperature 60°C (140°F) and engine running time delays that are dependent on manifold air temperature and vehicle speeds above 5 mph have been met.
^ There are three diagnostics associated with this sensor:
- Code 14 coolant temperature sensor high.
- Code 15 coolant temperature sensor low.
- Code 73 intermittent coolant temperature.
The Fail-safe actions are:
^ A default value is used and it is a function of engine running time or manifold air temperature.
^ Allows VCC operation.

CRUISE CONTROL
^ When engaged, alters the shift pattern to reduce the number of 3-4 and 4-3 shifts.
A time limit must be met between 3-2 and a 2-3.
A time limit must be met between 4-3 and a 3-4.

ENGINE SPEED
^ Determined by the ignition module.
^ Used to regulate the PWM solenoid duty cycle.

BRAKE SWITCH
^ Controls the VCC solenoid and inputs into the PCM.
^ Disengages the VCC solenoid from the power feed source when the brake is applied.
^ There is one diagnostics associated with this switch.
- Code 90 VCC brake switch problem.
^ Detects when a change of state should have occurred and it did not the fail-safe actions are:
^ No cruise control.
It will recover once the switch changes state.

PRNDL SWITCH
^ It is mounted on the manual shaft lever and it gives transmission range based upon lever position.
^ Inputs the selected transmission range into the PCM.
^ Controls shift solenoid state.
^ It is an assembly of four switches that connect to ground.
^ There is one diagnostics associated with this switch.
- Code 91 PRNDL switches problem.
^ Detects the 9 false combinations.
^ Checks the P/N discrete on starting or in fourth gear.
The fail-safe actions are:
^ Use the D4 shift schedules.
^ VCC PWM solenoid will be regulated incorrectly in D3 recovers upon a valid range.
If not properly aligned between D4 and D3 no VCC may occur should set a code if not properly aligned or in wrong range manual LO may not be attainable.