P063D
P063D-GENERATOR VOLTAGE SENSE HIGH
For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams. Electrical Diagrams
Theory of Operation
There are two communication lines between the ECM and generator. Based on sensed battery voltage, the ECM commands the generator to charge the batteries to a desired voltage. The max voltage the ECM will command the generator to charge is 14.75-Volts. The ECM then receives feedback from the generator on the voltage level it is charging the batteries. The ECM will not light a MIL lamp for this fault, but the ETC lamp will be on solid.
- When Monitored:
Engine running.
- Set Condition:
Charging voltage exceeds battery voltage by more than a calibrated amount for a calibratable period of time.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.
1. OTHER DTCS
NOTE: Batteries must be fully charged and capable of passing a battery load test. The generator belt tension must be within specification. Inspect the vehicle for any aftermarket equipment that may exceed the maximum generator output.
1. Ignition on, engine not running.
2. Using the scan tool, read DTCs.
Are there any other charging related faults?
Yes
- Go to and perform the appropriate diagnostic procedure.
No
- Go To 2
2. SHORT CIRCUIT BETWEEN THE AUXILIARY BATTERY AND THE ECM
1. Using the scan tool, monitor battery voltage in the ECM module.
2. Measure battery voltage of the primary battery (one that powers ECM) using a Voltmeter.
Is the reported voltage from the scan tool equal to both battery voltages?
Yes
- Go To 3
No
- Repair or replace open/short circuit in harness from battery to ECM.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
3. CIRCUIT BETWEEN THE PRIMARY BATTERY AND THE AUXILIARY BATTERY
1. Turn the ignition off.
2. Using a Voltmeter, measure battery voltage of the auxiliary battery (one that generator charges).
Is the measured voltage of the auxiliary battery equal to the measured voltage of the primary battery? NOTE: Primary battery voltage was measured in step 2.
Yes
- Go To 6
No
- Go To 4
4. OPEN CIRCUIT BETWEEN THE PRIMARY BATTERY AND THE AUXILIARY BATTERY
1. Disconnect the positive battery cables from both the primary and auxiliary battery.
2. Disconnect the cable that connects the primary battery to the auxiliary battery.
NOTE: Check connectors - Clean/repair as necessary.
3. Measure the resistance in the cable that connects the primary battery to the auxiliary battery.
Is the resistance less than 10.0 Ohms?
Yes
- Go To 5
No
- Repair/replace open circuit in the wiring harness.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
5. SHORT CIRCUIT BETWEEN THE GENERATOR AND PRIMARY BATTERY
1. Turn the ignition off.
2. Disconnect the positive battery cables from both the primary and auxiliary battery.
3. Disconnect the battery cable that connects the primary battery to the auxiliary battery.
NOTE: Check connectors - Clean/repair as necessary.
4. Measure the resistance between each end of the harness and battery ground.
Is the measured resistance greater than 10k Ohms?
Yes
- Go To 6
No
- Repair/replace short circuit in the wiring harness.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
6. OPEN CIRCUIT BETWEEN THE GENERATOR AND PRIMARY BATTERY
1. Measure the resistance in the harness that connects the auxiliary battery to the generator.
Is the resistance less than 10.0 Ohms?
Yes
- Go To 7
No
- Repair/replace open circuit in the wiring harness.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
7. ECM
1. Disconnect the generator harness connector.
2. Disconnect the power cable from the generator stud to the auxiliary battery.
NOTE: Check connectors - Clean/repair as necessary.
3. Measure the resistance between the generator output stud and the generator Sense circuit in the generator harness connector.
Is the resistance less than 10.0 Ohms?
Yes
- Replace the ECM.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
No
- Replace the Generator.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.