P0626
DTC P0625 or P0626
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 Descriptors
DTC P0625
- Generator F-Terminal Circuit Low Voltage
DTC P0626
- Generator F-Terminal Circuit High Voltage
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 ignition is ON and the engine is OFF, the ECM should detect a duty cycle near 0%. When the engine is running, the duty cycle should be between 5-99%.
Conditions for Running the DTC
P0625
* The engine is running.
* The engine speed is less than 3 000 RPM.
P0626
* The engine is not running.
* The ignition is in the ON position.
Conditions for Setting the DTC
P0625
The ECM detects a pulse width modulated (PWM) signal less than 5% for 15 s.
P0626
The ECM detects a pulse width modulated (PWM) signal greater than 65% for 15 s.
Action Taken When the DTC Sets
DTC P0625 and P0626 are C type DTCs.
Conditions for Clearing the DTC
DTC P0625 and P0626 are C type DTCs.
Reference Information
Schematic Reference
Starting and Charging Schematics Electrical Diagrams
Connector End View Reference
Component Connector End Views A/C Compressor Clutch
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
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Programming and Relearning for scan tool information
Circuit/System Verification
1. Engine running.
2. Verify the scan tool GEN-F Terminal Signal Circuit parameter changes between 5 and 99 percent.
• If the parameter does not change
Refer to Circuit/System Testing.
• If the parameter changes
3. All OK.
Circuit/System Testing
1. Verify a test lamp illuminates between the G13 generator B+ circuit terminal X2 B+ and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Disconnect the B+ cable at the G13 generator.
2. Test for less than 2 ohms in the B+ circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Test for infinite resistance between the B+ circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
2. Test for infinite resistance between the signal circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the G13 generator.
• If the test lamp illuminates
2. Ignition OFF, disconnect the X1 harness connector at the G13 generator.
3. Verify the scan tool ECM GEN-F parameter is less than 5 percent.
• If 5 percent or greater
1. Ignition ON.
2. Test for less than 1 V between the signal circuit terminal 2 and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K20 engine control module.
• If less than 5 percent
4. Install a 3 A fused jumper wire between the signal circuit terminal 2 and B+.
5. Verify the scan tool ECM GEN-F Terminal Signal parameter is greater than 95 percent.
• If 95 percent or less
1. Ignition OFF, disconnect the harness connector at the K20 engine control module.
2. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms
3. Test for infinite resistance between the signal circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K20 engine control module.
• If greater than 95 percent.
6. Replace the G13 generator.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Generator Replacement Service and Repair
* Control Module References Programming and Relearning for ECM replacement, setup and programming