PCM and Input Information

The Powertrain Control Module (PCM) is an electronic device which monitors various input sensors within its control program. The PCM can then process a variety of transmission output functions and devices.

The PCM gathers data from the following electrical sensors, switches and solenoids:
- Automatic Transmission Fluid Temperature (TFT) sensor
- Automatic Transmission Fluid Pressure Manual Valve (TFP Val) Position switch assembly
- Engine Coolant Temperature (ECT) sensor
- Throttle Position (TP) sensor
- Brake switch

The PCM controls various transmission functions including the following:
- Shift quality
- Torque Converter Clutch (TCC) apply and release
- Line pressure
- Transmission diagnostics

The PCM is located underneath the hood on the left inner fender well.

The PCM has an internal FLASH EEPROM that is non-removable. This FLASH EEPROM must be programmed when you replace the PCM. For complete FLASH EEPROM programming procedures and service precautions, refer to POWERTRAIN CONTROL MODULE.

The Powertrain Control Module (PCM) is equipped with a self diagnostic feature that detects system failures and aids the technician in locating a faulty circuit. The PCM has memory for comparing various input information to programmed information. These conditions are described on the support page for each Diagnostic Trouble Code (DTC). If a value is not within the PCM parameters, a DTC will set and the default values or actions will be used, if applicable.

The PCM continually performs a self diagnostic check. You can use a scan tool in order to request the PCM to display any stored DTC. You cannot flash the DTC by grounding the DLC!

Important: Refer to STRATEGY BASED DIAGNOSTICS before beginning any diagnosis.

Important: Always refer to the POWERTRAIN ON BOARD DIAGNOSIS (OBD) SYSTEM CHECK before diagnosing any DTC.

The scan tool displays all stored DTCs and Freeze Frame or Failure Records in current and history status. If the DTC is in history status, the condition may be intermittent. An intermittent DTC is one which will not reset during the current ignition cycle. The support page of a DTC contains Diagnostic Aids to help locate intermittent conditions.

When diagnosing specific DTCs, always diagnose and repair the first DTC set. After you have made the repair and the DTC is cleared, road test the vehicle and check for DTCs to reset. A failed component or circuit often causes other related components and circuits to display faulty information or to set a false DTC.

Each DTC has a specific diagnostic table and support page. The diagnostic table contains a series of tests that pinpoint a specific failure. The support page contains a circuit description, a list of enable conditions that must be met to set the code, a Diagnostic Aids section to help locate intermittent conditions, and a test description section that identifies specific steps in the DTC table. The table and the support page were designed to be used together so that you will better understand the circuit and the diagnostic procedure.

If a visual check does not locate the cause of the fault, test the suspected circuit with J 39200 DMM. Use J 39200 to check for the following opens and shorts:
- Short to voltage-connect J 39200 DMM to a known good ground on the DC voltage scale.
- Short to ground-Connect J 39200 DMM to a known good battery voltage on the DC voltage scale.
- Open circuit-Connect J 39200 DMM to each end of the circuit on the ohms scale with voltage removed from the circuit.

For a complete test description and procedure, refer to ELECTRICAL DIAGNOSIS.