P2503

P2503-CHARGING SYSTEM OUTPUT 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 alternator to charge the batteries to a desired voltage. The max voltage the PCM 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:
While the engine is running.

- Set Condition:
Battery voltage is less than 11.5 Volts for more than eight seconds. Battery voltage must exceed 12.0 Volts for more than five seconds for fault to become inactive.





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

1. ACTIVE DTC
1. With the scan tool, read DTCs.

Is DTC P065A active?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test

2. CHECK THE GENERATOR
1. Turn the ignition off.
2. Disconnect the Generator field harness connector.

NOTE: Check connectors - Clean/repair as necessary.

3. Measure the resistance between the Generator field terminals at the Generator.

Is the resistance between 0.5 and 15.0 Ohms?

Yes

- Go To 3

No

- Replace the Generator.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

3. CHECK THE (K20) GENERATOR FIELD CONTROL CIRCUIT FOR A SHORT TO GROUND
1. Disconnect the PCM C1 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

2. Measure the resistance between ground and the (K20) Generator Field Control circuit at the Generator field harness connector.

Is the resistance below 10k Ohms?

Yes

- Repair the (K20) Generator Field Control circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 4

4. CHECK THE (K20) GENERATOR FIELD CONTROL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Measure the resistance between of the (K20) Generator Field Control circuit between the Generator field harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 5

No

- Repair the (K20) Generator Field Control circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

5. POWERTRAIN CONTROL MODULE
1. Measure and record the voltage between battery positive circuit of the PCM harness connector and the battery negative circuits of the PCM harness connector.
2. Reconnect the PCM connectors.
3. Using the scan tool, read battery voltage.
4. Compare the voltage reading from the voltmeter with that of the scan tool.

Are the readings within 3.0 Volts of each other?

Yes

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test

No

- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.