1. Turn the ignition OFF.
2. Depress the brake pedal and inspect the center high mounted stop lamp (CHMSL).

Does the CHMSL light?

--

Go to Step 2

Go to Step 6

Remove and inspect the VEH STOP fuse.

Is the fuse open?

--

Go to Step 13

Go to Step 3

1. Re-install the VEH STOP fuse.
2. Disconnect C1 at the rear lamps bussing block.
3. Connect a test lamp from terminal B to ground.
4. Depress the brake pedal while looking at the test lamp.

Does the test lamp light?

--

Go to Step 5

Go to Step 4

Locate and repair the open in CKT 1320 (LT BLU) between the rear lamps bussing block and the underhood bussed electrical center (UBEC).

Is the repair complete?

--

System OK

--

Locate and repair the open in CKT 1750 (BLK) between the rear lamps bussing block and ground.

Is the repair complete?

--

System OK

--

Remove and inspect the STOP LPS fuse.

Is the fuse open?

--

Go to Step 7

Go to Step 8

Locate and repair the short to ground in the following circuits.

Replace the fuse.

Is the repair complete?

--

System OK

--

1. Re-install the fuse.
2. Connect a test lamp from (back probe) terminal B of the stoplamp switch to ground.

Does the test lamp light?

--

Go to Step 10

Go to Step 9

Locate and repair the open in CKT 1540 (ORN) between the stoplamp switch and the fuse.

Is the repair complete?

--

System OK

--

1. Connect a test lamp from (back probe) terminal A to ground.
2. While probing, depress the brake pedal.

Does the test lamp light?

--

Go to Step 12

Go to Step 11

Replace the stoplamp switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes.

Is the repair complete?

--

System OK

--

Locate and repair the open in CKT 17 (WHT) between the stoplamp switch and the UBEC.

Is the repair complete?

--

System OK

--

Locate and repair the short to ground in CKT 1320 (LT BLU).

Is the repair complete?

--

System OK

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