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DTC P0625 or P0626

DTC P0625 or 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 Descriptors

DTC P0625

Generator F-Terminal Circuit Low Voltage

DTC P0626

Generator F-Terminal Circuit High Voltage

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
B+

P0625

P0625

-

-

Signal

P0625

P0625

P0626

-

Control

P0621

P0621

P0621

-



Circuit/System Description

The engine control module (ECM) 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 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 status of the generator field duty cycle signal circuit. When the ignition is ON and the engine is OFF, the ECM should detect a duty cycle near 0%. When the engine is running, the duty cycle should be between 5-99%.

Conditions for Running the DTC


P0625

• The engine is running.

• The engine speed is less than 3 000 RPM.



P0626

• The engine is not running.

• The ignition is in the ON position.


Conditions for Setting the DTC

P0625

The ECM detects a pulse width modulated (PWM) signal less than 5% for 15 s.

P0626

The ECM detects a pulse width modulated (PWM) signal greater than 65% for 15 s.

Action Taken When the DTC Sets

DTC P0625 and P0626 are C type DTCs.

Conditions for Clearing the DTC

DTC P0625 and P0626 are C type DTCs.

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 Verification

Engine running, observe the scan tool Generator F-Terminal Signal Circuit parameter. The Generator F-Terminal Signal Circuit parameter should display between 5-99%.

Circuit/System Testing


1. Verify that a test lamp illuminates between the G13 Generator B+ terminal A X1 and ground.

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

3. Ignition OFF, disconnect the X2 harness connector at the G13 Generator.

4. Ignition ON, verify the scan tool Generator F-Terminal Signal parameter displays less than 5%.

5. If greater than the specified range, test the signal circuit terminal 2 for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.

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

7. Verify the scan tool Generator F-Terminal Signal parameter displays greater than 95%.

8. 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 K20 Engine Control Module.

9. If the circuit tests normal replace the G13 Generator.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Refer to Generator Replacement (Diesel) Generator Replacement (LAU/A28NER) Generator Replacement (LLU/A16LET) Generator Replacement (LHU/A20NFT) .

• Control Module References for ECM replacement, setup, and programming