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
Typical Scan Tool Data
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 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 5-99 percent.
Conditions for Running the DTC
* The engine is running.
* The system voltage is between 9.5-18 V.
Conditions for Setting the DTC
The ECM detects that the generator field duty cycle signal is less than 5 percent for 30 seconds.
Action Taken When the DTC Sets
The charge indicator turns ON.
Conditions for Clearing the DTC
* The DTC will pass when the generator field duty cycle signal is greater than 5 percent for 1 second.
* The charge indicator will turn OFF when the DTC passes or is cleared with a scan tool.
* A 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)
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)
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 reading should be less than 5%.
2. Engine running, observe the scan tool ECM GEN-F Terminal Signal parameter. The reading should be greater than 5%.
Circuit/System Testing
1. Verify that a test lamp illuminates between the B+ circuit terminal 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 is less than 5%.
• If greater than the specified range, test the signal circuit terminal 2 or C X1 for a short to voltage. If the circuit tests normal, replace the ECM.
4. Install a 3 A fused jumper wire between the signal circuit terminal 2 or C X1 and B+. Verify the scan tool ECM GEN-F Terminal Signal is greater than 95%.
• If less than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
5. 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 (LE5) (Generator Replacement)Generator Replacement (LY7) (Generator Replacement)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming.