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 Descriptor
DTC P0622: Generator F-Terminal CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
B+ | P0622 | P0622 | -- | -- |
Field Duty Cycle Signal | P0622 | P0622 | -- | -- |
Charge Indicator Signal | P0621 | -- | P0621 | -- |
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: Engine running. Parameter Normal Range: 5-99% | |||
B+ | 0% | 0% | -- |
Field Duty Cycle Signal | 0% | 0% | 99% |
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 percent. When the engine is running, the duty cycle should be between 5-99 percent.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The engine speed is less than 3000 RPM. |
| • | No generator, crankshaft, or camshaft position sensor DTCs are set. |
Conditions for Setting the DTC
One of the following conditions exist:
| • | The engine is OFF, and the GEN F-Terminal Signal is greater than 65 percent for 15 seconds. |
| • | The engine is running, and the GEN F-Terminal Signal is less than 5 percent for 30 seconds. |
Action Taken When the DTC Sets
| • | The charge indicator turns ON. |
| • | The driver information center (DIC) displays the SERVICE BATTERY CHARGING SYSTEM message. |
Conditions for Clearing the DTC
| • | The DTC will pass when the condition for setting the DTC is no longer present. |
| • | A history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The charge indicator and DIC message will remain ON until the DTC passes or is cleared, even if the ignition is cycled. |
Reference Information
Schematic Reference
Starting and Charging Schematics
Connector End View Reference
Description and Operation
Charging System Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, engine OFF, observe the scan tool ECM GEN-F Terminal Signal parameter. The reading should be less than 5 percent.
- Engine running, observe the scan tool ECM GEN-F Terminal Signal parameter. The reading should be greater than 5 percent.
Circuit/System Testing
- Verify that a test lamp illuminates between the B+ circuit ring terminal 1 X2 and ground.
- Ignition OFF, disconnect the X1 harness connector at the generator.
- Ignition ON, verify the scan tool ECM GEN-F Terminal Signal parameter is less than 5 percent.
- Install a 3A fused jumper wire between the field duty cycle circuit terminal 2 X1 and B+. Verify the scan tool ECM GEN-F Terminal Signal parameter is greater than 95 percent.
- If all circuits test normal, test or replace the generator.
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
| ⇒ | If greater than the specified range, test the field duty cycle circuit terminal 2 X1 for a short to voltage. If the circuit tests normal, replace the ECM. |
| ⇒ | 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
