GM Service Manual Online
For 1990-2009 cars only

Step

Action

Values

Yes

No

1

Inspect the stoplamps.

Do the stop lamps work?

--

Go to Step 3

Go to Step 2

2

Repair the stoplamps before completing this diagnostic table.

Does the CHMSL work after the stoplamps have been repaired?

--

System OK

Go to Step 3

3

  1. Remove the CHMSL lamp bulb. Refer to High Mount Stop Lamp Replacement .
  2. Visually and physically inspect the CHMSL lamp bulb.

Is the lamp bulb defective?

--

Go to Step 4

Go to Step 5

4

Replace the CHMSL lamp bulb. Refer to High Mount Stop Lamp Replacement .

Is the repair complete?

--

System OK

--

5

  1. Disconnect the CHMSL connector.
  2. Use an ohmmeter to measure the resistance between ground and the BK wire in the CHMSL connector.

Is the resistance equal to the specified value?

0 ohms

Go to Step 7

Go to Step 6

6

Repair the open circuit between ground and the BK wire in the CHMSL connector.

Is the repair complete?

--

System OK

--

7

Repair the open circuit between the stoplamp switch and the CHMSL.

Is the repair complete?

--

System OK

--