2010 Cadillac CTS Sedan AWD V6-3.0L Page 1523
瀚慖f the test lamp is always ON, test the control circuit for short to voltage. If the circuit tests normal, replace the K20 ECM.
瀚慖f the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace
the K20 ECM.
5. If all circuits tests normal, replace the KR27 starter relay.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) (See: Power and Ground Distribution/Power Distribution Relay/Service and Repair/Relay
Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (See: Power and Ground Distribution/Power
Distribution Relay/Service and Repair/Relay Replacement (Within an Electrical Center))
* Control Module References (See: Testing and Inspection/Programming and Relearning)for ECM replacement, setup, and programming
P0621
DTC P0621
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 Descriptor
DTC P0621
- Generator L-Terminal Circuit
Diagnostic Fault Information
Circuit/System Description
The engine control module (ECM) uses the generator turn ON control circuit to control the load of the generator on the engine. A high side driver
in the ECM applies a voltage to the voltage regulator. This controls the voltage regulator to turn the field circuit ON and OFF. The ECM monitors
the state of the generator turn ON control circuit. The ECM should detect low voltage on generator turn on control circuit when the ignition is ON
and the engine is OFF, or when the charging system malfunctions. With the engine running, the ECM should detect high voltage on the generator
turn on control circuit.
Conditions for Running the DTC
* The ignition ON, engine OFF for ignition on test.
* The engine is running for the run test.
Conditions for Setting the DTC
* During the ignition on test, the ECM detects voltage on the generator turn on control circuit for 5 seconds.
* During the run test, the ECM detects low voltage on the generator turn on control circuit for 15 seconds.
Action Taken When the DTC Sets
DTC P0621 is a C type DTC.
Conditions for Clearing the DTC
