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DTC P0626

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    • Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0626: Generator F-Terminal Circuit High Voltage

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Alternator F-Terminal

P0625

P0625

P0626

-

Circuit/System Description

The engine control module (ECM) uses the alternator field duty cycle signal circuit to monitor the duty cycle of the alternator and fault indication. The alternator field duty cycle signal circuit connects to the high side of the field winding in the alternator. A pulse width modulated (PWM) high side driver in the voltage regulator turns the field winding ON and OFF. The ECM uses the PWM signal input to determine the generator load on the engine. This allows the ECM to adjust the idle speed to compensate for high electrical loads.

The ECM monitors the state of the alternator field duty cycle signal circuit. When the engine is running, the ECM should detect a duty cycle that varies up to 100 percent. The ECM monitors the PWM signal using an Ignition ON test and a RUN test. During the tests, if the ECM detects an out of range PWM signal, a DTC will set.

Conditions for Running the DTC

    • The engine is not running.
    • The ignition is in the ON position.

Conditions for Setting the DTC

The ECM detects a pulse width modulated (PWM) signal greater than 65 percent for at least 15 seconds.

Action Taken When the DTC Sets

DTC P0626 is a C type DTC.

Conditions for Clearing the DTC

DTC P0626 is a C type DTC.

Reference Information

Schematic Reference

Starting and Charging Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Charging System Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the generator.
  2. Ignition ON, engine OFF, observe the scan tool ECM GEN-F Terminal Signal parameter. It should display less than 10 percent.
  3. If the GEN-F Terminal Signal parameter was not affected by the disconnected alternator harness, test the GEN-F Terminal Signal circuit terminal 2 for a short to voltage. If the circuit tests normal, replace the ECM.
    If the circuit tested normal and the ECM parameter changed from above 65 percent to less than 10 percent, replace the alternator.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    • Control Module References for ECM replacement, setup, and programming
    •  Generator Replacement : LNQ → LF1 → LE5
   


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