P0622

DTC P0622

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



DTC Descriptor
DTC P0622
- Generator F-Terminal Circuit




Diagnostic Fault Information






Circuit/System Description

The engine control module (ECM) uses the generator field duty cycle signal 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 key 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 between 5-95 percent.


Conditions for Running the DTC

* The vehicle speed is greater than 8 km/h (5 mph).
* The system voltage is between 9.5-18 volts.



Conditions for Setting the DTC

* The ECM detects a PWM signal greater than 65 percent for 5 seconds during the KEY ON test.
* The ECM detects a PWM signal less than 5 percent for 15 seconds during the RUN test.



Action Taken When the DTC Sets

* The ECM will command the charge indicator to be illuminated on the instrument panel cluster (IPC).
* The driver information center (DIC) will display the CHECK CHARGE SYSTEM message.
* The ECM will not illuminate the malfunction indicator lamp (MIL).
* The ECM will store conditions, which were present when the DTC set as Fail Records data only.



Conditions for Clearing the DTC

* The ECM will command the indicator and message OFF after one trip in which the diagnostic test has been run and passed.
* The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.



Reference Information

Schematic Reference

Starting and Charging Schematics ([1][2]Electrical Diagrams)

Connector End View Reference

Component Connector End Views (Connector Views)


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)


Scan Tool Reference

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


Circuit/System Verification

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


Circuit/System Testing

1. Ignition OFF. Disconnect the generator harness connector.
2. With the ignition ON, and the engine OFF, connect a test lamp to battery positive voltage and repeatedly probe the generator field duty cycle circuit, harness side, while monitoring the GEN-F Terminal Signal Parameter in the ECM data list with a scan tool. Verify that the scan tool parameter changes from 0 percent to greater than 95 percent.

• If the GEN-F Terminal Signal scan tool parameter was not affected by the test lamp, then test the GEN-F Terminal Signal circuit for a short to voltage, a short to ground, a high resistance, an open circuit. If the circuit tests normal, then replace the ECM.

3. If the circuit tests normal during the Ignition ON / Run tests, and the scan tool parameter changed from 0 percent to greater than 95 percent, then replace the generator.



Repair Instructions

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

* Control Module References (Programming and Relearning)for ECM replacement, setup, and programming
* Generator Replacement (LZ4) (Generator Replacement)Generator Replacement (LY7) (Generator Replacement)for generator replacement