P2503 CHARGING SYSTEM OUTPUT LOW

When Monitored and Set Condition:

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

DIAGNOSTIC PROCEDURE

NOTE: Refer to VERIFICATION TESTS for appropriate verification test procedures.

1. With the DRBIII®, read DTCs. Is DTC P2502 set?
   Yes --> Repair other DTCs first. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
   No --> Go To 2
2. Disconnect the Generator field harness connector.
   NOTE: Check connectors - Clean/repair as necessary.
   Measure the resistance between the generator field terminals at the generator. Is the resistance between .5 and 15 Ohms?
   Yes --> Go To 3
   No --> Replace the generator. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
3. 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. Is the resistance greater than 100 ohms?
   Yes --> Go To 4
   No --> Repair the generator field driver circuit shorted to ground. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
4. 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 DRBIII® to measure and record battery voltage. Compare the voltage reading from the voltmeter with that of the DRBIII®. Are the readings within 3 volts of each other?
   Yes --> Refer to the SYMPTOM: INTERMITTENT CONDITION Symptom (Diagnostic Procedure). Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
   No --> Replace and program the ECM in accordance with the Service Information. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).