P2502 CHARGING SYSTEM ERROR

When Monitored and Set Condition:

When Monitored: While the engine is running.
Set Condition: The ECM cycles the voltage regulator in the generator while monitoring for a change in output voltage. If the voltage does not drop when the regulator is off, the fault is set.

POSSIBLE CAUSES

• DIRTY OR LOOSE CONNECTIONS
• HIGH RESISTANCE IN THE B+ CIRCUIT
• HIGH RESISTANCE IN THE B+ CROSS OVER CABLE
• HIGH RESISTANCE IN THE GROUND CIRCUIT
• GENERATOR
• ECM
• INTERMITTENT CONDITION

DIAGNOIST PROCEDURE

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

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 POWERTRAIN VERIFICATION TEST VER - 4 (DIESEL).
2. Measure the voltage between the B+ post of the generator and the B+ post of the battery while the engine is running. Is the voltage above .4 volts?
   Yes --> Repair the high resistance in the B+ circuit from battery to the generator. Perform POWERTRAIN VERIFICATION TEST VER - 4 (DIESEL).
   No --> Go To 3
3. Measure the voltage between the B+ post of the generator and the B+ post of the right side battery to the left side battery while the engine is running. Is the voltage above .4 volts?
   Yes --> Repair the high resistance in the B+ cross over cable from right side battery to left side battery. Perform POWERTRAIN VERIFICATION TEST VER - 4 (DIESEL).
   No --> Go To 4
4. Measure the voltage between the generator case and the B- post of the battery. Is the voltage above .1 volts?
   Yes --> Repair the high resistance in the ground circuit. Perform POWERTRAIN VERIFICATION TEST VER - 4 (DIESEL).
   No --> Go To 5
5. Disconnect the Generator field harness connector.
   NOTE: Check connectors - Clean/repair as necessary.
   Measure the resistance between the generator field terminals. Is the resistance between .5 and 15 Ohms?
   Yes --> Go To 6
   No --> Replace the generator. Perform POWERTRAIN VERIFICATION TEST VER - 4 (DIESEL).
6. Turn the ignition off. Reconnect the Generator field harness connector. Disconnect the ECM harness connectors.
   NOTE: Check connectors - Clean/repair as necessary.
   Ignition on, engine not running. Measure and record the voltage between battery positive circuits of the ECM harness connector and the battery negative circuits of the ECM harness connector. Turn the ignition off. Reconnect the ECM harness connectors. Start the engine. 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 --> Test Complete.
   No --> Replace and program the ECM in accordance with the Service Information. Perform POWERTRAIN VERIFICATION TEST VER - 4 (DIESEL).