GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

  1. Using a test light, backprobe between C420 terminal A and ground.
  2. Depress and hold the brake pedal.

Does the test light illuminate?

--

Go to Step 3

Go to Step 2

2

Repair a poor connection or an open in circuit 17 between S304 and C420 terminal A.

Has the repair been made?

--

Go to Exterior Lights System Check

--

3

Using a test light, backprobe between the C240 terminal A and terminal B.

Does the test light illuminate

--

Go to Step 5

Go to Step 4

4

Repair a poor connection in circuit 350 between S416 and G402.

Has the repair been made?

--

Go to Exterior Lights System Check

--

5

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

Has the repair been made?

--

Go to Exterior Lights System Check

--