GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Blazer - 4WD 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Service Indicator Always On

Circuit Description

The SERVICE 4WD indicator is located in the instrument cluster. It receives ignition voltage from a 10 amp gage fuse through the instrument cluster feed circuit. This circuit also supplies all of the gages with ignition voltage. The transfer case shift control module controls the SERVICE 4WD indicator by sending the instrument cluster a Class 2 message. This lamp may be controlled with the scan tool using the instrument cluster device controls.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step determines whether the failure is the result of a faulty transfer case shift control module or the instrument cluster.

Step

Action

Yes

No

Schematic Reference: Transfer Case Control Schematics

Connector End View Reference: Transfer Case Control Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Turn the ignition ON, with the engine OFF.
  2. Install a scan tool.
  3. Using a scan tool, command the SERVICE 4WD indicator OFF.

Does the SERVICE 4WD indicator turn OFF?

Go to Step 3

Go to Instrument Cluster Replacement in Instrument Panel, Gages and Console

3

Replace the transfer case shift control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the repair?

Go to Step 4

--

4
  1. Use the scan tool in order to clear the DTCs .
  2. Operate the vehicle in order to determine if the symptom has been corrected.

Is the symptom still present?

Go to Step 2

System OK