P063A
P063A-GENERATOR VOLTAGE SENSE CIRCUIT
Special Tools:
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 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. Pre-Diagnostic Troubleshooting Procedure.
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.
1. Ignition on, engine not running.
2. With the scan tool, select View DTCs.
3. Start the engine.
4. Allow the idle to stabilize.
5. With the scan tool, View DTCs.
Is the DTC Active at this time?
Yes
- Go To 2
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test
2. EXCESSIVE RESISTANCE IN THE (A804) GENERATOR SENSE CIRCUIT
1. Turn the ignition off.
2. Disconnect the Generator harness connector.
3. 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 the PCM Pinout Box (8815A) to perform diagnosis.
4. Measure the resistance of the (A804) Generator Sense circuit from the Generator harness connector to the appropriate terminal of PCM Pinout Box.
Is the resistance below 5.0 Ohms?
Yes
- Go To 3
No
- Repair the excessive resistance in the (A804) Generator Sense circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
3. (A804) GENERATOR SENSE CIRCUIT SHORTED TO GROUND
1. Measure the resistance between ground and the (A804) Generator Sense circuit at the Generator harness connector.
Is the resistance below 100 Ohms?
Yes
- Repair the short to ground in the (A804) Generator Sense circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 4
4. GENERATOR OPERATION
1. Connect the C1 PCM harness connector.
2. Using a 12-volt test light connected to ground, probe the (K20) Generator Field Control circuit in the Generator Field harness connector.
3. Ignition on, engine not running.
4. With the 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.
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.