GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Blazer - 4WD 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Transfer Case Shift Control Switch Indicator Always On - Two or More

Circuit Description

The indicator lamps circuit consists of 3 individual lamps contained inside their respective buttons making up the transfer case shift control switch assembly. They are the 2HI, 4HI and 4LO indicators. When the ignition switch is placed in the RUN position, current is provided to the switch assembly. The transfer case shift control module (TCCM) provides a ground for the indicators when a particular gear is active or when the transfer case is in transition. Through solid state circuity located inside the switch assembly, voltage can be regulated to provide less illumination when the headlamps or parking lights are turned ON.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step helps to determine intermittent conditions.

    2.

  2. This step helps to determine if the TCCM is commanding more than one indicator ON.

    3.

  3. This step tests and repairs a short to ground in the indicator control circuits.

    4.

  4. This step tests if more than one indicator control circuits are shorted together.

Switch Indicator Lamps Remain ON - Two or More

Step

Action

Yes

No

Schematic Reference: Transfer Case Control Schematics

1

Important: The transfer case shift control module is not a class 2 device. A scan tool cannot be utilized on this transfer case.

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Cycle the ignition switch from ON to OFF and wait 10 seconds.
  2. Start the vehicle and drive.

Do 2 or more switch indicator lamps still remain ON?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

3

  1. Turn OFF the ignition.
  2. Disconnect the connectors at TCCM.
  3. Turn ON the ignition, with the engine OFF.

Do all the switch indicator lamps stay OFF?

Go to Step 5

Go to Step 4

4

Repair a short to ground on the suspect indicator control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 6

5

Test the suspect indicator control circuits to determine if they are shorted together. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 7

6

Replace the shift control switch. Refer to Transfer Case Shift Control Switch Replacement .

Did you complete the replacement?

Go to Step 8

--

7

Replace the TCCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 8

--

8

Operate the vehicle in order to determine if the symptom has been corrected.

Is the symptom still present?

Go to Step 2

System OK