P0626

DTC P0625 or P0626

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category

DTC Descriptors

DTC P0625

-
Generator F Terminal Low Voltage

DTC P0626

-
Generator F Terminal High Voltage

Circuit/System Description

The engine control module (ECM) uses the alternator field duty cycle signal circuit to monitor the duty cycle of the alternator. The alternator field duty cycle signal circuit connects to high side of the field windings in the alternator. A pulse width modulated (PWM) high side driver in the voltage regulator turns the field windings ON and OFF. The ECM uses the PWM signal input to determine the alternator load on the engine. This allows the ECM to adjust the idle speed to compensate for high electrical loads. The ECM monitors the status of the alternator field duty cycle signal circuit. When the key is in the RUN position and the engine is OFF, the ECM should detect a duty cycle near 0 percent. When the engine is running, the duty cycle should be between 5-95 percent.

Conditions for Running the DTC

* The vehicle speed is above 8 km/h (5 mph).

* The system voltage is between 9.5-18 V.

Conditions for Setting the DTC

With the engine running, the ECM detects a PWM signal less than 5 percent for at least 15 seconds.

Action Taken when the DTC Sets

DTC's P0625 and P0626 are type C Store Only DTCs

Conditions for Clearing the MIL/DTC

DTC's P0625 and P0626 are type C Store Only DTCs

Reference Information

Schematic Reference

Starting and Charging Schematics Electrical Diagrams

Connector End View Reference

Component Connector End Views Fuel Pump and Level Sensor Assembly

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

With the scan tool installed, ignition ON and the engine running, observe the alternator-F Terminal Signal parameter in the ECM data list. The alternator-F Terminal Signal parameter should read between 5 and 95 percent.

Circuit/System Testing

1. Verify that a test lamp illuminates between the generator B+ circuit terminal 1 X2 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

2. Ignition OFF, disconnect the X1 harness connector at the generator.

3. Ignition ON, verify the scan tool ECM GEN-F Terminal Signal parameter displays less than 5 percent.

• If greater than the specified range, test the signal circuit terminal 2 for a short to voltage. If the circuit tests normal, replace the ECM.

4. Install a 3 A fused jumper wire between B+ and the signal circuit terminal 2.

5. Verify the scan tool ECM GEN-F Terminal Signal parameter displays greater than 95 percent.

• If less than the specified range, test the signal circuit terminal 2 for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

6. If the circuit tests normal replace the generator.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Generator Replacement (L77) Generator ReplacementGenerator Replacement (LFX) Generator Replacement

* Control Module References Control Module References for module replacement, setup, and programming