GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you review the Audible Warnings Description and perform the necessary inspections?

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Go to Step 2

Go to Diagnostic Starting Point

2

  1. Insert the key in the ignition.
  2. Turn the ignition switch to the RUN position.
  3. Using a scan tool, enter BCM Data List INPUT 2.
  4. Monitor the left turn signal and the right turn signal.
  5. Move the turn signal switch to the LEFT and the RIGHT positions.

Does the scan tool alternate between ON and OFF for both parameters in relation to the turn signal switch position?

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Go to Step 3

Go to Step 7

3

  1. Drive the vehicle with the scan tool installed.
  2. Enter BCM Data List DATA.
  3. Monitor the vehicle speed.

Is the vehicle speed displayed for the vehicle in motion?

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Go to Step 4

Go to Step 9

4

Inspect the connections at the BCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Are the connections in need of repair?

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Go to Step 5

Go to Step 6

5

Repair the connections at the BCM as necessary. Refer to Connector Repairs in Wiring Systems.

Did you complete the repair?

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Go to Step 10

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6

Replace the BCM. Refer to Body Control Module Replacement in Body Control System.

Did you complete the replacement?

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Go to Step 10

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7

  1. Using a digital multimeter (DMM), backprobe the BCM connector C1 terminal B6 (left turn signal) and terminal B7 (right turn signal) to ground.
  2. Select the 40 Volt Range.
  3. Measure the voltage.
  4. Turn ON the ignition, with the engine OFF.
  5. Operate the turn signal switch.
  6. With the turn signals operating, push the MIN/MAX button 4 times.
  7. Avg. is displayed at the top of the meter.

Is approximately 1/2 battery voltage displayed on both terminals?

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Go to Step 4

Go to Step 8

8

Repair the open or the high resistance in CKT 14 or 15. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

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Go to Step 10

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9

Repair the open or the high resistance in CKT 389. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

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Go to Step 10

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10

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 2