P063C
P063C-GENERATOR VOLTAGE SENSE LOW
For a complete wiring diagram, refer to the Wiring Information.
Theory of Operation
There are two communication lines between the Powertrain Control Module (PCM) and Generator. Based on sensed battery voltage, the PCM commands the Generator to charge the batteries to a desired voltage. The max voltage the EPCM will command the Generator to charge is 14.75 Volts. The PCM then receives feedback from the Generator on the voltage level it is charging the batteries. The PCM will not light a MIL lamp for this fault.
- When Monitored:
Engine running.
- Set Condition:
Battery voltage exceeds charging 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. BATTERY TERMINALS DAMAGED, CORRODED, OR LOOSE CONNECTIONS
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. Visually inspect the positive and negative connections at the battery. Visually inspect the battery negative connections at the engine block.
Are the connections free of corrosion and are they tight?
Yes
- Go To 2
No
- Clean and/or tighten the connections.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
2. CHECK THE (A804) GENERATOR SENSE CIRCUIT FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Disconnect the Generator harness connector.
3. Disconnect the PCM C1 harness connector.
NOTE: Check connectors - Clean/repair as necessary.
4. Measure the resistance between the (A804) Generator Sense circuit at the PCM C1 harness connector and ground.
Is the resistance above 10k Ohms?
Yes
- Go To 3
No
- Repair the (A804) Generator Sense circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
3. CHECK THE (A804) GENERATOR SENSE CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Measure the resistance of the (A804) Generator Sense circuit between the Generator harness connector to the PCM C1 harness connector.
Is the resistance below 5.0 Ohms?
Yes
- Go To 4
No
- Repair the (A804) Generator Sense circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
4. CHECK FOR AN OPEN CIRCUIT BETWEEN GENERATOR AND AUXILIARY BATTERY
1. Disconnect the positive battery cables from both the primary and auxiliary battery.
2. Disconnect the harness from the auxiliary battery to the Generator.
3. Measure the resistance in the harness that connects the auxiliary battery to the Generator.
Is the resistance below 5.0 Ohms?
Yes
- Go To 5
No
- Repair/replace open positive battery cable in wiring harness.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
5. CHECK THE GENERATOR
1. Measure the resistance between the Generator output stud and the generator Sense circuit on the Generator connector.
NOTE: There should be approximately 2.4k Ohms resistance.
Does the resistance measure approximately 2.4k Ohms?
Yes
- Replace Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
No
- Replace Generator.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.