P0622

P0622-GENERATOR FIELD NOT SWITCHING PROPERLY

P0622 - Generator Field Not Switching Properly:

WHEN MONITORED
When the ignition is on.

SET CONDITION
The feedback signal does not match the commanded signal for the voltage regulator.

POSSIBLE CAUSES
- Generator
- Open driver circuit
- GEN source shorted to battery negative
- (K20) Field driver circuit shorted to voltage
- GEN source open
- ECM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test

1. GENERATOR
Turn the ignition off.
Disconnect the Generator field harness connector.
Check connectors - Clean/repair as necessary.
Measure the resistance between the generator field terminals.

Q: Is the resistance between 0.5 and 15 Ohms?

YES: Go To 2
NO: Replace the Generator. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1

2. OPEN DRIVER CIRCUIT





Disconnect the ECM harness connectors.
Check connectors - Clean/repair as necessary.
Measure the resistance of the generator driver wire between the generator harness connector and the ECM harness connector.

Q: Is the resistance less than 10 ohms.

YES: Go To 3
NO: Repair the open driver circuit. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1

3. GENERATOR FIELD CIRCUIT OPEN




Measure the resistance of the generator field return circuit between the generator harness connector and battery negative.

Q: Is the resistance less than 10 ohms.

NO: Repair the Generator field return shorted to Battery negative. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1

YES: Go To 4

4. FIELD DRIVER CIRCUIT SHORTED TO VOLTAGE





Measure the voltage between the (K20) generator field driver circuit in the generator harness connector and battery negative.

Q: Is the voltage greater than 1 volt?

YES: Repair the (K20) Generator field driver circuit shorted to voltage.
NO: Go To 5

5. ECM
While monitoring with scan tool, connect a jumper wire between the driver circuit and the return circuit in the alternator connector.

Q: Did the DTC return?

YES: Replace the ECM. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
NO: Repair complete. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1