P0622

DTC P0622

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 Descriptor
DTC P0622
- Generator F-Terminal Circuit

Diagnostic Fault Information





Typical Scan Tool Data





Circuit 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 the high side of the field winding in the generator. 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 generator field duty cycle signal circuit. When the ignition is in the RUN position and the engine is OFF, the ECM should detect a duty cycle near 0 percent. However, when the engine is running, the duty cycle should be 5-100 percent.

Conditions for Running the DTC

* The ignition is ON.
* No generator, crankshaft position (CKP) sensors, or camshaft position (CMP) sensor DTCs are set.

Conditions for Setting the DTC

* Ignition ON engine OFF, the ECM detects a PWM signal greater than 65 percent for 5 seconds
* Engine running, the ECM detects a PWM signal less than 5 percent for 15 seconds.

Action Taken When the DTC Sets

DTC P0622 is a type C DTC.

Conditions for Clearing the DTC

DTC P0622 is a type C DTC.

Reference Information
Schematic Reference

Starting and Charging Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Charging System Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Ignition ON, engine OFF, observe the scan tool ECM GEN-F Terminal Signal parameter. The parameter should read 0%.
2. Engine running, observe the scan tool ECM GEN-F Terminal Signal parameter. The parameter should read between 5 and 99%.

Circuit/System Testing

1. Verify that a test lamp illuminates between the B+ circuit terminal A 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 connectors at the generator and GBCM.
3. Ignition ON, verify the scan tool ECM GEN-F Terminal Signal parameter is 0%.

• If greater than the specified value, test the field duty cycle signal circuit terminal 2 X1 for a short to voltage. If the circuit tests normal, replace the ECM.

4. Connect a test lamp between the field duty cycle signal circuit terminal 2 X1 of the generator harness and B+. Verify the scan tool ECM GEN-F Terminal Signal parameter is greater than 95%.

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

5. Reconnect the GBCM harness connector. Disconnect the test lamp.
6. Ignition ON, verify the scan tool ECM GEN-F Terminal Signal parameter is 0%.

• If greater than the specified value, replace the GBCM.

7. Connect a test lamp between the field duty cycle circuit terminal 2 X1 of the generator harness and B+. Verify the scan tool ECM GEN-F Terminal Signal parameter is greater than 95%.

• If less than the specified range, replace the GBCM.

8. If all circuits test normal, test or replace the generator.

Repair Instructions

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

* Generator Replacement (LLR) (Generator Replacement)Generator Replacement (LH8) (Generator Replacement)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming.