P2503
P2503-CHARGING SYSTEM OUTPUT LOWP2503 - Charging System Output Low:
WHEN MONITORED
While the engine is running.
SET CONDITION
The battery voltage exceeds target voltage by more than a calibrated value.
POSSIBLE CAUSES
- Other DTC's present
- Generator
- Field driver circuit shorted to ground
- ECM
- Intermittent condition
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
Diagnostic Test
1. OTHER DTC'S PRESENT
With the scan tool, read DTCs.
Q: Is DTC P2502 set?
YES: Repair other DTC's first. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
NO: Go To 2
2. GENERATOR
Disconnect the Generator field harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance between the generator field terminals at the generator.
Q: Is the resistance between .5 and 15 Ohms?
YES: Go To 3
NO: Replace the generator. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
3. FIELD DRIVER CIRCUIT SHORTED TO GROUND
Disconnect the ECM harness connectors.
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance of the generator field driver circuit between the generator and battery negative.
Q: Is the resistance greater than 100 ohms?
YES: Go To 4
NO: Repair the generator field driver circuit shorted to ground. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
4. ECM
Measure and record the voltage between battery positive circuit of the ECM harness connector and the battery negative circuits of the ECM harness connector.
Reconnect the ECM connectors.
Use the scan tool to measure and record battery voltage.
Compare the voltage reading from the voltmeter with that of the scan tool.
Q: Are the readings within 3 volts of each other?
YES: Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure).
NO: Replace and program the ECM in accordance with the Service Information. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1