P2504

P2504-CHARGING SYSTEM OUTPUT HIGH

For a complete wiring diagram, refer to the Wiring Information.

The Powertrain Control module (PCM) uses the generator field duty cycle signal circuit or F-terminal circuit, to monitor the duty cycle of the generator. The generator field duty cycle signal circuit connects to high side of the field windings in the generator. A Pulse Width Modulated (PWM) high side driver in the voltage regulator turns the field windings ON and OFF. The PCM uses the PWM signal input to determine the generator load on the engine. This allows the PCM to adjust the idle speed to compensate for high electrical loads. The PCM monitors the status of the generator field duty cycle signal circuit. When the key is in the RUN position and the engine is OFF, the PCM should detect a duty cycle near 0 percent. However, when the engine is running, the duty cycle should be between 5-95 percent.

- When Monitored:
The engine running. The engine speed greater than 1157 RPM.

- Set Condition:
The PCM compares sensed battery voltage with the Generator Sense circuit voltage. If the Generator Sense circuit voltage if greater than sensed battery voltage, this DTC will set. One Trip Fault. Three good trips to turn off the MIL.

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

1. DTC IS ACTIVE

NOTE: Inspect the vehicle for aftermarket accessories that may exceed the Generator system output.

NOTE: Inspect the Generator harness connector and the Generator eyelet for corrosion or damage before continuing.

NOTE: Inspect the condition and tension of the Generator belt before continuing.

NOTE: Inspect the battery before continuing.

1. Ignition on, engine not running.
2. With the scan tool, select View DTCs. Record DTC and Freeze Frame information
3. With the scan tool, clear DTCs.
4. Start the engine and allow it to reach operating temperature.
5. With the scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test

2. EXCESSIVE RESISTANCE IN THE B(+) CIRCUIT

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

NOTE: Make sure all test equipment and cables are clear of any belts, pulleys or other moving parts.

1. Perform a voltage drop test between the generator B(+) output terminal and the battery positive (+) post.
2. Start the engine.

Is the voltage above 0.4 Volts?

Yes

- Repair the battery positive (+) circuit between the generator and battery for high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 3

3. EXCESSIVE RESISTANCE BETWEEN THE GENERATOR CASE AND GROUND

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

1. Perform a voltage drop test between the generator case and battery ground (-) post.
2. Start the engine and allow it to reach operating temperature.

Is the voltage above 0.1 of a Volt?

Yes

- Repair the excessive resistance in the Generator case ground.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 4

4. (A804) GEN SENSE CIRCUIT SHORTED TO VOLTAGE

1. Turn the ignition off.
2. Disconnect the Generator harness connector.
3. Disconnect the Powertrain Control Module (PCM) harness connector.
4. Turn the ignition on.
5. Measure the voltage of the (K20) Gen Field Control circuit.

Is there any voltage present?

Yes

- Repair the (K20) Gen Field Control circuit for a short to voltage.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 6

6. GENERATOR

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

1. Turn the ignition off.
2. Connect the Generator harness connector.
3. Connect the Powertrain Control Module (PCM) harness connector.
4. Perform a voltage drop test between the Generator Eyelet terminal and the (A804) Gen Sense circuit in the Generator harness connector.
5. Start the engine and allow it to reach operating temperature.

Is the voltage above 0.1 of a Volt?

Yes

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

No

- Go To 7

7. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Generator and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
5. Look for the data to change or for the DTC to reset during the wiggle test.
6. Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module (PCM). PCM/ECM/TCM Reprogramming
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.