P2503-CHARGING SYSTEM OUTPUT LOW

For a complete wiring diagram Refer to Section 8W.

When Monitored:
With the engine speed greater than 1157 RPM.
Set Condition:
The 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.

Possible Causes

EXCESSIVE RESISTANCE IN THE B(+) CIRCUIT BETWEEN THE GENERATOR AND THE BATTERY

EXCESSIVE RESISTANCE BETWEEN THE GENERATOR CASE AND GROUND

(K20) GEN FIELD CONTROL CIRCUIT SHORTED TO VOLTAGE

(K20) GEN FIELD CONTROL CIRCUIT SHORTED TO GROUND

(K20) GEN FIELD CONTROL CIRCUIT OPEN OR HIGH RESISTANCE

(A804) GEN SENSE CIRCUIT OPEN OR HIGH RESISTANCE

GENERATOR

POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Diagnostic Test

1. DTC IS ACTIVE

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.

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

Is the status Active for this DTC?

Yes

Go to 2

Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

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 can result in personal injury or death.

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

Monitor the voltage between the generator B(+) output terminal and the battery positive (+) post.
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 PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 3

3. EXCESSIVE RESISTANCE BETWEEN THE GENERATOR CASE AND GROUND

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

Monitor the voltage between the generator case and battery ground (-) post.
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 Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 4

4. (K20) GEN FIELD CONTROL CIRCUIT SHORTED TO VOLTAGE

Turn the ignition off.
Disconnect the Generator harness connector.
Disconnect the Powertrain Control Module (PCM) harness connector.
Turn the ignition on.
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 PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 5

5. (K20) GEN FIELD CONTROL CIRCUIT SHORTED TO GROUND

Turn the ignition off.
Measure the resistance between ground and the (K20) Gen Field Control circuit in the Generator harness connector.

Is the resistance below 100 ohms?

Yes

Repair the short to ground in the (K20) Gen Field Control circuit.

Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 6

6. (K20) GEN FIELD CONTROL CIRCUIT OPEN OR HIGH RESISTANCE

Measure the resistance of the (K20) Gen Field Control circuit between the Generator harness connector and the Powertrain Control Module (PCM) harness connector.

Is the resistance below 5.0 ohms?

Yes

Go to 7

Repair the open in the (K20) Gen Field Control circuit.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)

7. (A804) GEN SENSE CIRCUIT OPEN OR HIGH RESISTANCE

Measure the resistance of the (A804) Gen Sense between the Generator harness connector and the Powertrain Control Module (PCM) harness connector.

Is the resistance above 5.0 ohms?

Yes

Go to 8

Repair the (A804) Gen Sense circuit for an open circuit or high resistance.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)

8. GENERATOR

Turn the ignition off.
Connect the Powertrain Control Module (PCM) harness connector.
Turn the ignition on.
With a scan tool, actuate the Generator Field to toggle on and off.
Using a 12-volt test light connected to ground, check the (K20) Gen 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 in accordance with the Service Information.

Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 9

9. POWERTRAIN CONTROL MODULE (PCM)

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

Were any problems found?

Yes

Repair as necessary.

Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).