2010 Cadillac CTS Sedan AWD V6-3.0L Page 1523

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