GM Service Manual Online
For 1990-2009 cars only

Stop Lamps Inoperative - Center High Mounted Domestic/Canada

Center High Mount Stop Lamp Inoperative (Dom/Can)

Step

Action

Value(s)

Yes

No

1

Were you sent here from the Exterior Lights System Check?

--

Go to Step 2

Go to Exterior Lights System Check

2

  1. Using a DMM, backprobe between the connector C140 terminal F and ground.
  2. Depress the brake pedal.
  3. Measure the available voltage at the connector.

Is the measured voltage within the specified values?

10.0-14.0V

Go to Step 8

Go to Step 3

3

  1. Using a DMM, backprobe between the underhood electrical center connector C3 terminal A1 and ground.
  2. Depress the brake pedal.
  3. Measure the available voltage at the connector.

Is the measured voltage within the specified values?

10.0-14.0V

Go to Step 4

Go to Step 5

4

Repair a poor connection or an open in CKT 20 between the underhood electrical center connector C3 terminal A1 and connector C140 terminal F.

Is the repair complete?

--

Go to Exterior Lights System Check

--

5

  1. Using a DMM, backprobe between the underhood electrical center connector C2 terminal F1 and ground.
  2. Depress the brake pedal.
  3. Measure the available voltage at the connector.

Is the measured voltage within the specified values?

10.0-14.0V

Go to Step 7

Go to Step 6

6

Repair a poor connection or an open in CKT 20 between the stop lamp switch connector C2 terminal B and the underhood electrical center connector C2 terminal F1.

Is the repair complete?

--

Go to Exterior Lights System Check

--

7

Replace the underhood electrical center.

Is the repair complete?

--

Go to Exterior Lights System Check

--

8

  1. Using a DMM, backprobe between the center high mounted stoplamp (CHMSL) connector terminal A and ground.
  2. Depress the brake pedal.
  3. Measure the available voltage at the connector.

Is the measured voltage within the specified values?

10.0-14.0V

Go to Step 10

Go to Step 9

9

Repair a poor connection or an open in CKT 820.

Is the repair complete?

--

Go to Exterior Lights System Check

--

10

  1. Connect a DMM between the CHMSL connector terminal A and terminal B.
  2. Depress the brake pedal.
  3. Measure the available voltage at the connector.

Is the measured voltage within the specified values?

10.0-14.0V

Go to Step 12

Go to Step 11

11

Repair a poor connection or an open in CKT 150 between the CHMSL and G401.

Is the repair complete?

--

Go to Exterior Lights System Check

--

12

Replace the CHMSL.

Refer to High Mount Stop Lamp Replacement .

Is the repair complete?

--

Go to Exterior Lights System Check

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