P0622

P0622-GENERATOR FIELD CONTROL CIRCUIT

P0622-Generator Field Control Circuit:

WHEN MONITORED
With the ignition on. Engine running.

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.

POSSIBLE CAUSES
- (K20) GEN field control circuit shorted to battery voltage
- (K20) GEN field control circuit open
- (K20) GEN field control circuit shorted to ground
- (Z20) Ground circuit open
- Generator
- PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test

1. ACTIVE DTC

Ignition on, engine not running.
With a scan tool, read DTCs.

Q: Is the DTC active at this time?

YES: Go To 2
NO: Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition
Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test




2. GENERATOR OPERATION

Turn the ignition off.
Disconnect the Generator Field harness connector.
Using a 12-volt test light, jump it across the Generator Field harness connector.
Ignition on, engine not running.
With the scan tool, actuate the Generator Field Control circuit.

Q: Does the test light illuminate brightly and flash on and off?

YES: Replace the Generator. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 3




3. (K20) GEN FIELD CIRCUIT SHORTED BATTERY VOLTAGE

Turn the ignition off.
Disconnect the PCM harness connectors
Ignition on, engine not running.
Measure the voltage on the (K20) Gen Field Control circuit in the Generator Field harness connector.

Q: Is the voltage above 1.0 volt?

YES: Repair the short to battery voltage in the (K20) Gen Field Control circuit. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 4




4. (K20) GEN FIELD CIRCUIT OPEN

Turn the ignition off.

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 from the Generator Field harness connector to appropriate terminal of the special tool #8815.

Q: Is the resistance below 5.0 ohms?

YES: Go To 5
NO: Repair the open in the (K20) Gen Field Control circuit. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test




5. (K20) GEN FIELD CIRCUIT SHORTED TO GROUND

Measure the resistance between ground and the (K20) Gen Field Control circuit in the Generator Field harness connector.

Q: Is the resistance below 100 ohms?

YES: Repair the short to ground in the (K20) Gen Field Control circuit. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 6




6. (Z20) GROUND CIRCUIT OPEN

Measure the resistance between the (Z20) Ground circuit in the Gen Field harness connector and ground.

Q: Does the test light illuminate brightly?

YES: Go To 7
NO: Repair the open in the (Z20) Ground circuit. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

7. PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

Q: Were there any problems found?

YES: Repair as necessary. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Replace and program the Powertrain Control Module. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test