GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

  1. Turn the ignition to the engine OFF position.
  2. Turn the left turn signal ON.

Does the turn signal function properly?

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Go to Step 2

Go to Turn Signal Lamps Inoperative - Left or Right Side

2

  1. Connect a scan tool.
  2. Using the scan tool, read the left turn signal input in the body control module (BCM).

Does the scan tool show ON?

--

Go to Step 3

Go to Step 6

3

  1. Disconnect the instrument cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gauges and Console.
  2. Connect a test lamp from terminal B1 to ground.

Does the test lamp light or flash?

--

Go to Step 4

Go to Step 5

4

  1. Inspect the instrument cluster printed circuit and the left turn signal indicator filament.
  2. Repair as needed. Refer to Instrument Cluster Bulb Replacement in Instrument Panel, Gauges and Console.

Did you find and correct the condition?

--

System OK

Go to Step 7

5

Locate and repair CKT 14 (LT BLU) between the mid bussed electrical center (MBEC) and the instrument cluster.

Is the repair complete?

--

System OK

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6

Locate and repair the open in CKT 14 (LT BLU) between the MBEC and the BCM.

If no open is found, replace the BCM. Refer to Body Control Module Replacement in Body Control Systems.

Is the repair complete?

--

Go to Step 3

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7

Locate and repair the open to ground in CKT 1850 (BLK).

Is the repair complete?

--

System OK

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