P063A

P063A-GENERATOR VOLTAGE SENSE CIRCUIT





For a complete wiring diagram refer to Diagrams/Electrical.

- When Monitored:

The engine running. The engine speed greater than 1157 RPM.

- Set Condition:

The PCM recognizes the alternator output voltage is less than the Battery feed circuit voltage. One trip failure. The Generator light will illuminate. The fault will be checked again on the next key cycle.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test

1. ACTIVE DTC

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

NOTE: The battery must be fully charged.

NOTE: The Generator belt tension and condition must be checked before continuing.

Ignition on, engine not running.

With a scan tool, select View DTCs.

Start the engine.

Allow the idle to stabilize.

With the scan tool, View DTCs.

Is the DTC Active at this time?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

2. EXCESSIVE RESISTANCE IN THE (A803) GENERATOR SENSE CIRCUIT





Turn the ignition off.

Disconnect the Generator harness connector.

Disconnect the C1 PCM harness connector.

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 Miller Special Tool #8815 to perform diagnosis.

Measure the resistance of the (A803) Generator Sense circuit from the Generator harness connector to the appropriate terminal of special tool #8815.

Is the resistance below 5.0 ohms?

Yes

- Go To 3

No

- Repair the excessive resistance in the (A803) Generator Sense circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

3. (A803) GENERATOR SENSE CIRCUIT SHORTED TO GROUND





Measure the resistance between ground and the (A803) Generator Sense circuit at the Generator harness connector.

Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (A803) Generator Sense circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 4

4. GENERATOR OPERATION





Connect the C1 PCM harness connector.

Using a 12-volt test light connected to ground, probe the (K20) Generator Field Control circuit in the Generator Field harness connector.

Ignition on, engine not running.

With a scan tool, actuate the Generator Field Driver.

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.

Does the test light illuminate brightly and flash on and off?

Yes

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

No

- Go To 5

5. PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

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.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test