2010 Cadillac CTS Sedan AWD V6-3.0L Page 1528
Engine running, observe the scan tool GEN-F Terminal Signal parameter. The GEN-F Terminal Signal parameter should display between 5-99
percent.
Circuit/System Testing
1. Verify that a test lamp illuminates between the generator B+ output circuit X2 terminal B and ground.
瀚慖f 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 parameter displays less than 5 percent.
瀚慖f greater than the specified range, test the signal circuit terminal 2 for a short to voltage. If the circuit tests normal, replace the K20 ECM.
4. Install a 3 A fused jumper wire between B+ and the signal circuit.
5. Verify the scan tool ECM GEN-F Terminal Signal parameter displays greater than 95 percent.
瀚慖f less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace
the K20 ECM.
6. If the circuit tests normal replace the G13 generator.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Generator Replacement (LF1/LLT) (See: Starting and Charging/Charging System/Alternator/Service and Repair)Generator Replacement
(LSA) (See: Starting and Charging/Charging System/Alternator/Service and Repair)
* Control Module References (See: Testing and Inspection/Programming and Relearning)for ECM replacement, setup, and programming
P0626
DTC P0625 or P0626
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/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 percent. When the engine is
running, the duty cycle should be between 5-99 percent.
