P0622

P0622-GENERATOR FIELD CONTROL CIRCUIT/OPEN





For a complete wiring diagram refer to the Wiring Information Electrical Diagrams.

Theory of Operation

There are two communication lines between the ECM and alternator. Based on sensed battery voltage, the ECM commands the alternator to charge the batteries to a desired voltage. The max voltage the ECM will command the alternator to charge is 14.75 volts. The ECM then receives feedback from the alternator on the voltage level it is charging the batteries through a sense line. The ECM will not light a MIL lamp for this fault.

- When Monitored:
When the ignition is on.

- Set Condition:
The feedback signal does not match the commanded signal for the voltage regulator.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure

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

Is the resistance between.5 and 15 Ohms?

Yes

- Go To 2

No

- Replace the Generator.
- Perform POWERTRAIN VERIFICATION TEST (DIESEL). Powertrain Verification Test

2. (K20) GEN FIELD CONTROL CIRCUIT OPEN
1. Disconnect the ECM harness connectors.
2. Check connectors - Clean/repair as necessary.
3. Measure the resistance of the (K20) Gen Field Control circuit between the Generator harness connector and the ECM harness connector.

Is the resistance less than 10 ohms.

Yes

- Go To 3

No

- Repair the open in the (K20) Gen Field Control circuit.
- Perform POWERTRAIN VERIFICATION TEST (DIESEL). Powertrain Verification Test

3. GENERATOR FIELD OPEN
1. Measure the resistance of the generator field return circuit between the generator harness connector and battery negative.

Is the resistance less than 10 ohms.

No

- Repair the Generator field return shorted to Battery negative.
- Perform POWERTRAIN VERIFICATION TEST (DIESEL). Powertrain Verification Test

Yes

- Go To 4

4. (K20) GEN FIELD CONTROL CIRCUIT SHORTED TO VOLTAGE
1. Measure the voltage on the (K20) Gen Field Control circuit at the Generator harness connector.

Is the voltage greater than 1 volt?

Yes

- Repair the short to voltage in the (K20) Gen Field Control circuit.

No

- Go To 5

5. ECM
1. While monitoring with scan tool, connect a jumper wire between the (K20) Gen Field Control circuit and the (A804) Gen Sense circuit in the alternator connector.

Did the DTC return?

Yes

- Replace the ECM.
- Perform POWERTRAIN VERIFICATION TEST (DIESEL). Powertrain Verification Test

No

- Repair complete.
- Perform POWERTRAIN VERIFICATION TEST (DIESEL). Powertrain Verification Test