GM Service Manual Online
For 1990-2009 cars
Makes 🢒 Chevrolet 🢒 2004 🢒 C-Series Medium Duty Truck C6/7/8 - Mexico 🢒 Body 🢒 Lighting Systems 🢒 Stop Lamps Inoperative

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

1

Did you review the exterior lighting description and operation and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Lighting Systems

2
  1. Press down the brake pedal.
  2. Apply the trailer brake hand control valve - Super Chassis w/JE4 and RQ3/U86.

Do the stop lamps illuminate?

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

Go to Step 3

3

Is the vehicle being worked on a Super Chassis w/JE4 and RQ3/U86?

Go to Step 4

Go to Step 5

4

Are the stop lamps inoperative from the trailer brake hand control valve only?

Go to Step 16

Go to Step 5

5
  1. Remove the stop lamp relay.
  2. Probe the stop lamp switch signal circuit of the stop lamp relay 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 9

Go to Step 6

6
  1. Disconnect the stop lamp switch.
  2. Probe the battery positive voltage circuit of the stop lamp switch with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 23

7
  1. Connect a 20 amp fused jumper wire between the battery positive voltage circuit of the stop lamp switch and the stop lamp switch signal circuit of the stop lamp switch.
  2. Probe the stop lamp switch signal circuit of the stop lamp relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 19

Go to Step 8

8

Does the fuse in the jumper wire open?

Go to Step 24

Go to Step 25

9
  1. Connect a test lamp between the stop lamp switch signal circuit of the stop lamp relay and the coil side ground circuit of the stop lamp relay.
  2. Press down the brake pedal.

Does the test lamp illuminate?

Go to Step 10

Go to Step 26

10

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

Do the stop lamps illuminate?

Go to Step 20

Go to Step 11

11

Does the fuse in the jumper wire open?

Go to Step 14

Go to Step 12

12
  1. Leave the fused jumper wire connected.
  2. Disconnect the turn signal switch.
  3. Probe the stop lamp supply voltage circuit of the turn signal switch with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 13

Go to Step 27

13
  1. Leave the fused jumper wire connected
  2. Connect a 20 amp fused jumper wire between the stop lamp supply voltage circuit of the turn signal switch and the left rear stop/turn lamp supply voltage circuit of the turn signal switch.

Does the left stop lamp illuminate?

Go to Step 21

Go to Step 28

14
  1. Disconnect the turn signal switch.
  2. Test the stop lamp supply voltage circuit for a short to ground between the stop lamp relay and the turn signal switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 36

Go to Step 15

15
  1. Disconnect both stop lamps.
  2. Test both stop lamp supply voltage circuits for a short to ground between the turn signal switch and the stop lamps. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 36

Go to Step 34

16
  1. Disconnect the trailer stop lamps switch.
  2. Probe the battery positive voltage circuit of the trailer stop lamps switch with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 17

Go to Step 29

17

Connect a 20 amp fused jumper wire between the battery positive voltage circuit of the trailer stop lamps switch and the stop lamp switch signal circuit of the trailer stop lamps switch.

Do the stop lamps illuminate?

Go to Step 22

Go to Step 18

18

Does the fuse in the jumper wire open?

Go to Step 30

Go to Step 31

19

Inspect for poor connections at the harness connector of the stop lamps 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 36

Go to Step 32

20

Inspect for poor connections at the stop lamps relay. 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 36

Go to Step 33

21

Inspect for poor connections at the harness connector of the turn signal 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 36

Go to Step 34

22

Inspect for poor connections at the harness connector of the trailer stop lamps 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 36

Go to Step 35

23

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

Did you complete the repair?

Go to Step 36

--

24

Repair a short to ground in the stop lamp switch signal circuit of the stop lamps relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 36

--

25

Repair an open or high resistance in the stop lamp switch signal circuit of the stop lamps relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 36

--

26

Repair an open or high resistance in the stop lamps relay coil side ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 36

--

27

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

Did you complete the repair?

Go to Step 36

--

28

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

Did you complete the repair?

Go to Step 36

--

29

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

Did you complete the repair?

Go to Step 36

--

30

Repair a short to ground in the stop lamp switch signal circuit of the trailer stop lamps switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 36

--

31

Repair an open or high resistance in the stop lamp switch signal circuit of the trailer stop lamps switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 36

--

32

Replace the stop lamps switch. Refer to following:

    •  Stop Lamp Switch Replacement in Hydraulic Brakes or
    •  Stop Lamp Switch Replacement in Air Brakes

Did you complete the replacement?

Go to Step 36

--

33

Replace the stop lamps relay.

Did you complete the replacement?

Go to Step 36

--

34

Replace the turn signal switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column.

Did you complete the replacement?

Go to Step 36

--

35

Replace the trailer stop lamps switch. Refer to Trailer Stop Lamp Switch Replacement in Air Brakes.

Did you complete the replacement?

Go to Step 36

--

36

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3