P2503
P2503-CHARGING SYSTEM OUTPUT LOW
Special Tools:
For a complete wiring diagram, refer to the Wiring Information.
- When Monitored:
With the engine speed greater than 1157 RPM.
- Set Condition:
The Powertrain Control Module (PCM) detects that battery voltage is 1 volt below charging goal voltage for 13.47 seconds. The PCM compares sensed battery voltage with the field driver on and off. If the voltages are the same, this code will set. One Trip Fault. Three good trips to turn off the MIL.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. PCM Pre-Diagnostic Troubleshooting Procedure
Diagnostic Test
1. ACTIVE DTC
NOTE: Inspect the vehicle for aftermarket accessories that may exceed the generator system output.
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 a scan tool, select View DTCs. Record DTC and Freeze Frame information
3. With a 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 CHECKING FOR AN INTERMITTENT DTC diagnostic procedure. PCM Intermittent Condition Test.
2. CHECK FOR 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. Monitor the voltage between the Generator B+ output terminal and the battery positive (+) post.
2. Start the engine.
Is the voltage above 0.1 volts?
Yes
- Repair the battery positive (+) circuit between the generator and battery for high resistance.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 3
3. CHECK FOR 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.
NOTE: Make sure all Test. equipment and cables are clear of any belts, pulleys, or other moving parts.
1. Monitor the voltage 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 volts?
Yes
- Repair the excessive resistance in the Generator Case Ground.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 4
4. CHECK THE (K20) GENERATOR FIELD CONTROL CIRCUIT FOR A SHORT TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the Generator harness connector.
3. Disconnect the PCM C2 harness connector.
4. Turn the ignition on.
5. Measure the voltage of the (K20) Generator Field Control circuit.
Is there any voltage present?
Yes
- Repair the (K20) Generator Field Control circuit for a short to voltage.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 5
5. CHECK THE (K20) GENERATOR FIELD CONTROL CIRCUIT FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Measure the resistance between ground and the (K20) Generator Field Control circuit in the Generator harness connector.
Is the resistance above 10k Ohms?
Yes
- Go To 6
No
- Repair the (K20) Generator Field Control circuit for a short to ground.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
6. CHECK THE (K20) GENERATOR FIELD CONTROL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
CAUTION:
Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the GPEC Diagnostic Adaptor to perform the diagnosis.
1. Connect the (10436).
2. Measure the resistance of the (K20) Generator Field Control circuit between the Generator harness connector and the GPEC Adaptor.
Is the resistance below 5.0 Ohms?
Yes
- Go To 7
No
- Repair the (K20) Generator Field Control circuit for an open or high resistance.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
7. CHECK THE (A804) GENERATOR SENSE CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Measure the resistance of the (A804) Generator Sense between the Generator harness connector and the GPEC Adaptor.
Is the resistance below 5.0 Ohms?
Yes
- Go To 8
No
- Repair the (A804) Generator Sense circuit for an open or high resistance.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
8. GENERATOR
1. Turn the ignition off.
2. Reconnect the PCM C2 harness connector.
3. Turn the ignition on.
4. With a scan tool, actuate the Generator Field to toggle on and off.
5. Using a 12-volt test light connected to ground, check the (K20) Generator Field Control in the Generator harness connector.
NOTE: The test light should be illuminated and bright when toggled on. Compare the brightness to that of a direct connection to the battery.
Does the test light toggle on and off correctly during the actuator test?
Yes
- Replace the Generator.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 9
9. 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. Search for any Technical Service Bulletins that may apply.
Were any problems found?
Yes
- Repair as necessary.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
No
- Replace and program the Powertrain Control Module (PCM).
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.