Schematic Reference: Exterior Lights Schematics

Did you perform the Lighting System Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

Press down the brake pedal

Do all of the stop lamps illuminate?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

Is only one lamp inoperative?

Go to Step 4

Go to Step 5

1. Disconnect the inoperative stop lamp.
2. Probe the stop lamp supply voltage circuit of the inoperative lamp with a test lamp that is connected to a good ground.
3. Press down the brake pedal.

Does the test lamp illuminate?

Go to Step 17

Go to Step 18

Are all of the stop lamps, including the high mounted stop lamps, inoperative?

Go to Step 6

Go to Step 9

1. Disconnect the brake switch.
2. Probe the battery positive voltage circuit of the brake switch with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 19

Connect a 20 amp fused jumper wire between the battery positive voltage circuit of the brake switch and the stop lamp supply voltage circuit.

Do the stop lamps illuminate?

Go to Step 14

Go to Step 8

1. Leave the fused jumper wire connected.
2. Carefully backprobe pin A12 of C3 of the LH IP junction block with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 15

Go to Step 20

Are the high mounted stop lamps the only inoperative lamps?

Go to Step 10

Go to Step 12

1. Disconnect the high mounted stoplamp assembly.
2. Probe the stop lamp supply voltage circuit with a test lamp that is connected to a good ground.
3. Press down the brake pedal.

Does the test lamp illuminate?

Go to Step 11

Go to Step 21

1. Connect a test lamp between the stop lamp supply voltage circuit of the high mounted stop lamp assembly and the ground circuit of the high mounted stop lamp assembly.
2. Press down the brake pedal.

Does the test lamp illuminate?

Go to Step 16

Go to Step 22

1. Carefully backprobe the stop lamp supply voltage circuit of the inoperative lamps at the LH IP junction block with a test lamp that is connected to a good ground.
2. Press down the brake pedal.

Does the test lamp illuminate?

Go to Step 13

Go to Step 15

1. Disconnect the inoperative lamps.
2. Probe the stop lamp supply voltage circuit of the inoperative lamps with a test lamp that is connected to a good ground.
3. Press down the brake pedal.

Does the test lamp illuminate?

Go to Step 23

Go to Step 24

Inspect for poor connections at the harness connector of the brake switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 28

Go to Step 25

Inspect for poor connections at the harness connector of the LH IP junction block. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 28

Go to Step 26

Inspect for poor connections at the harness connector of the high mounted stop lamp assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 28

Go to Step 27

Repair an open or high resistance in the ground circuit of the inoperative lamp. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 28

--

Repair an open or high resistance in the stop lamp supply voltage circuit of the inoperative lamp. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 28

--

Repair an open, high resistance, or short to ground in the battery positive voltage circuit of the brake switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 28

--

Repair an open or high resistance in the stop lamp supply voltage circuit between the brake switch and the LH IP junction block. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 28

--

Repair an open or high resistance in the stop lamp supply voltage circuit between the high mounted stop lamp assembly and the LH IP junction block. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 28

--

Repair an open or high resistance in the ground circuit of the high mounted stop lamp assembly. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 28

--

Repair an open or high resistance in the ground circuit of the inoperative lamps. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 28

--

Repair an open or high resistance in the stoplamp supply voltage circuit of the inoperative lamps. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 28

--

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

Did you complete the replacement?

Go to Step 28

--

Replace the LH IP junction block. Refer to Instrument Panel Electrical Center or Junction Block Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 28

--

Replace the high mounted stop lamp assembly. Refer to High Mount Stop Lamp Replacement .

Did you complete the replacement?

Go to Step 28

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3