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
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 5-95 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 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 charge indicator 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 (Component Connector End Views)
Description and Operation
Charging System Description and Operation (Description and Operation)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Control Module References) for scan tool information
Circuit/System Verification
Engine running, observe the GEN-F Terminal Signal parameter in the ECM data list. The parameter should read between 5 and 95 percent.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the generator.
2. Ignition ON, engine OFF, connect a test lamp to B+ and repeatedly probe the generator field duty cycle circuit terminal 2, while monitoring the GEN-F Terminal Signal Parameter. The parameter should change from 0 percent to above 95 percent.
• If the parameter was not affected by the test lamp, test the circuit for a short to voltage, short to ground, or an open/high resistance. If the circuit tests normal, replace the ECM.
3. If the circuit tests normal, test or replace the generator.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Generator Replacement (With 4.2L Engine) ()Generator Replacement (5.3L Engine) (Generator Replacement (5.3L Engine))
* Control Module References (Control Module References) for ECM replacement, setup, and programming