P2503
P2503-CHARGING SYSTEM OUTPUT LOW
For a complete wiring diagram, refer to the Wiring Information.
Theory of operation
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 RPM is high enough to assure sufficient generator current output to satisfy the electrical loads.
- Set Condition:
The battery sensed voltage is less than the target charging voltage, during engine operation, for a calibrated amount of time. One Trip Fault. Generator light will illuminate.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.
1. ACTIVE DTC
NOTE: The battery must be fully charged.
1. Ignition on, engine not running.
2. With the scan tool, select View DTCs.
3. Read and record the related Freeze Frame data and DTCs.
4. With the scan tool, erase DTCs.
5. Start the engine.
6. Allow the idle to stabilize.
7. Ignition on, engine not running.
8. With the scan tool, select View DTCs.
Is the DTC Active at this time?
Yes
- Go To 3
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test
2. VISUAL INSPECTION
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: Inspect the vehicle for aftermarket accessories that may exceed the Generator System output.
NOTE: The Generator belt tension and condition must be checked before continuing.
Visually inspect the engine for any of the following conditions:
- Worn serpentine belt. Testing and Inspection.
- Binding Engine-Driven accessories: A/C Compressor, P/S Pump, Water pump.
- Misalignment of the Water pump, P/S Pump and A/C Compressor pulleys.
- Corroded PCM power and ground circuits.
Were any of the above conditions present?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 3
3. FUSED B+ CIRCUIT HIGH RESISTANCE
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 B+ Output Terminal and the Battery + Post.
Is the voltage above 0.4 of a Volt?
Yes
- Repair the excessive resistance in the battery positive circuit between the Generator and Battery.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 4
4. GENERATOR OPERATION
1. Turn the ignition off.
2. Disconnect the Generator Field harness connector.
3. Using a 12-volt test light connected to ground, probe (K20) Generator Field Control circuit in the Generator Field harness connector.
NOTE: The DTC needs to be cleared before actuating the Solenoid, if the DTC is not cleared, the Solenoid may not be allowed to actuate.
4. Ignition on, engine not running.
5. With the scan tool, actuate the Generator Field Driver.
NOTE: The test light should be illuminated and bright proportional to the maximum duty cycle allowed by the scan tool. For example, if the scan tool allows 100% actuation, the brightness should be as bright as a direct connection to the battery. If the scan tool allows a maximum 25% actuation, the brightness should be 25% as bright as a direct connection to the battery.
Does the test light illuminate accordingly during the actuation?
Yes
- Verify that there is good pin to terminal contact in the Generator and Powertrain Control Module connectors. Replace the Generator if no problems were found with the connectors. Generator - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 5
5. 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. Verify that there is good pin to terminal contact in the Generator and Powertrain Control Module connectors.
4. Perform any Technical Service Bulletins that may apply.
Were there any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Replace and program the Powertrain Control Module. PCM/ECM/TCM Reprogramming
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.