NGC

P0622-GENERATOR FIELD CONTROL CIRCUIT





For a complete wiring diagram Consult Diagrams/Electrical

- When Monitored:
With the engine running, battery voltage greater than 10.4 volts, and the Generator control active.

- Set Condition:
When the PCM tries to regulate the generator field with no result during monitoring. One Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.Initial Inspection and Diagnostic Overview

Diagnostic Test

1. DTC IS ACTIVE
Turn the ignition on.
With the scan tool, Clear DTCs in the Powertrain Control Module (PCM).
Start the engine and allow it to reach operating temperature.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

Increase engine speed by pressing the accelerator pedal. Do not exceed 3500 rpm.
With the scan tool, select View DTCs.
Is the DTC Active at this time?

Yes

- Go to 2

No

- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. Checking For An Intermittent DTC

2. (K20) GEN FIELD CONTROL CIRCUIT SHORTED TO GROUND




Turn the ignition off.
Disconnect the Generator connector.
Disconnect the C2 Powertrain Control Module (PCM) harness connector.
Measure the resistance between ground and the (K20) Gen Field Control circuit in the Generator harness connector.
Is the resistance above 100 ohms?

Yes

- Go to 3

No

- Repair the short to ground in the (K20) Gen Field Control circuit.
- Perform the PCM Verification Test. Powertrain Verification Test

3. (K20) GEN FIELD CONTROL CIRCUIT OPEN OR HIGH RESISTANCE




CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals, resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.

Measure the resistance of the (K20) Gen Field Control circuit between the Generator harness connector and the appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms?

Yes

- Go to 4

No

- Repair the open or high resistance in the (K20) Gen Field Control circuit.
- Perform the PCM Verification Test. Powertrain Verification Test

4. GENERATOR




Connect the C2 Powertrain Control Module (PCM) harness connector.
Turn the ignition on.
With the scan tool, actuate the Generator Field Control State.
Using a 12 volt test light connected to ground, check the (K20) Gen Field Control circuit in the Generator harness connector.

NOTE: The test light should be illuminated and bright proportional to the maximum duty cycle allowed by the scan tool. For example, if the scan tool allows 100% actuation, the brightness should be as bright as a direct connection to the battery. If the scan tool allows a maximum 25% actuation, the brightness should be 25% as bright as a direct connection to the battery.

Does the test light illuminate accordingly during the actuation?

Yes

- Replace the Generator.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Go to 5

5. POWERTRAIN CONTROL MODULE (PCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Generator and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Verify that there is good pin to terminal contact in the Generator and Powertrain Control Module connectors.
Look for broken, bent, pushed out or corroded terminals.
Search for any Technical Service Bulletins that may apply.
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Replace and program the Powertrain Control Module (PCM).
- Perform the PCM Verification Test. Powertrain Verification Test