Four-Wheel Drive Indicator Always On

Four-Wheel Drive Indicator Always On

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.

Circuit/System Description

The 4WD indicator lamp is located in the instrument cluster. Ignition 3 voltage is supplied to the instrument panel cluster (IPC) when the ignition switch is in the START or RUN position. When the vehicle is in START or RUN and the Engine control module (ECM) receives the axle switch signal from the front axle actuator, the ECM sends a CAN signal to the instrument cluster turning on the 4WD indicator. The 4WD indicator will stay on as long as the axle switch signal input is present.

Reference Information

Schematic Reference

Transfer Case Control Schematics MP 1222/1225/1226-NQG - Transfer Case

Connector End View Reference

Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)

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

Circuit/System Verification

1. Place the vehicle in 2WD install a scan tool and using engine data 2 look at the display for 2WD signal.

2. Verify that the scan tool indicates that the vehicle is in 2WD.

• If the scan tool indicates that the vehicle is in 4WD go to circuit system testing.

Circuit/System Testing

1. Check the axle switch signal circuit for a short to voltage.

• If everything checks normal then go to the next step.

2. Check the front axle actuator control circuit pin B at the front axle actuator connector or pin C at the transfer case shift control switch for a short to ground.

• If everything checks normal then short the axle actuator control circuit to ground this should cause the actuator to engage. Remove the short to ground and then short the circuit to ground again, this should cause the actuator to disengage. If the actuator does not operate properly then refer to front axle will not engage or front axle will not disengage. If everything checks normal go to ECM and IPC functionality check.

Instrument Panel Cluster (IPC) and Engine Control Module (ECM) Functionality

If all circuits referenced above check good use the scan tool under engine data 2 to see if the scan tool still indicates the vehicle is still in 4WD.

If the scan tool indicates the vehicle is in 4WD then replace the engine control module, if not then replace the IPC.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Instrument Cluster Replacement (With RPO SLT) Instrument Cluster Replacement (With RPO SLT)Instrument Cluster Replacement (Without RPO SLT) Instrument Cluster Replacement (Without RPO SLT)

* Engine Control Module Replacement Service and Repair for the 4.3L engine

* Engine Control Module Replacement Service and Repair for the 4.8L, 5.3L, 6.0L, and 6.2L engine

* Engine Control Module Replacement Service and Repair for the 6.6L engine

* Control Module References Control Module References for ECM replacement, setup, and programming

* Four-Wheel Drive Does Not Disengage Four-Wheel Drive Does Not Disengage

* Four-Wheel Drive Does Not Engage Four-Wheel Drive Does Not Engage