Pcm Diagnostic Trouble Codes
Before replacing the PCM for a failed driver, control circuit or ground circuit, be sure to check the related component/circuit integrity for failures not detected due to a double fault in the circuit. Most PCM driver/control circuit failures are caused by internal failures to components (i.e. relays and solenoids) and shorted circuits (i.e. sensor pull-ups, drivers and ground circuits). These faults are difficult to detect when a double fault has occurred and only one DTC has set. If the scan tool displays faults for multiple components (i.e.VSS, ECT, Batt Temp, etc.) identify and check the shared circuits for possible problems before continuing (i.e. sensor grounds or 5-volt supply circuits). Refer to the appropriate wiring diagrams to identify shared circuits. Refer to the appropriate Diesel Powertrain Diagnostic information.
The PCM supplies two regulated 5 volts supplies - a 5V primary and a 5V secondary (auxiliary) to the following sensors:
- 1. Camshaft Position Sensor (5V secondary)
- 2. Crankshaft Position Sensor (5V primary)
- 3. EGR Position feedback sensor (5V secondary) (if equipped)
- 4. Engine coolant temperature sensor (connected to 5V internal via a pullup resistor)
- 5. Inlet Air Temperature Sensor (connected to 5V internal via a pullup resistor)
- 6. Knock sensor (connected to 5V internal via a pullup resistor)
- 7. Manifold absolute pressure sensor (5V secondary)
- 8. Oil Pressure Switch (connected to 5V internal via pullup resistor)
- 9. Pedal Value Sensor #1 (5V Primary)
- 10. Pedal Value Sensor #2 (5V Secondary)
- 11. SRV Position Feedback Sensor (5V Secondary)
- 12. Throttle Position Sensors (5V Primary)
- 13. Variable Line Pressure Sensor (5V Secondary)