GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The resistance presented to the instrument cluster on terminal X1-28 is dependent upon the button selected on the trip computer switch. DTC 21 will set if the trip computer switch resistance is less than 1000 ohms for 100 milliseconds. The DTC is reset as soon as the switch resistance is greater than 1000 ohms. The DTC is logged as a History DTC.

Diagnostic Aids

By manipulating the harnesses at the various connectors it is often possible to isolate the cause of the circuit interruption. This harness can then be removed and repaired. Inspect for any damage to the harness, which could cause an intermittent open or short to earth or backed out terminals at the instrument cluster connectors, broken connector locks, improperly formed or damaged terminals. The multimeter allows continuity of the wiring harness circuit 894 to be checked.

DTC 21 - TRIP COMPUTER SWITCH VOLTAGE LOW

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn the ignition ON, with the engine OFF.

Can Tech 2 communicate with the body control module (BCM)?

--

Go to Step 3

Go to Diagnostic Starting Point - Computer/Integrating Systems

3

Inspect the switch for obvious signs of damage.

Is damage present?

--

Go to Step 4

Go to Step 5

4

Replace the trip computer switch. Refer to Driver Information Display Switch Replacement .

Did you complete the repair?

--

Go to Step 7

--

5

  1. Remove the instrument cluster.
  2. Connect an ohmmeter between the instrument cluster C3 mode circuit and a known good ground.

Is value as specified?

Less than 1 ohms

Go to Step 6

Go to Step 7

6

Repair short to ground in the trip computer mode circuit. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 7

--

7

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK