For 1990-2009 cars

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. Turn ON the ignition, with the engine OFF.
2. Observe the stop lamps.

Are the stop lamps OFF?

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

Go to Step 3

3 | Remove the stop lamps relay. Do the stop lamps remain illuminated? | Go to Step 4 | Go to Step 5
4 | Disconnect the turn signal switch. Do the stop lamps remain illuminated? | Go to Step 14 | Go to Step 15
5 | Probe the stop lamp switch signal circuit of the stop lamps relay with a test lamp that is connected to a good ground. Does the test lamp illuminate? | Go to Step 6 | Go to Step 11
6 |

1. Leave the test lamp connected.
2. Disconnect the stop lamps switch.

Does the test lamp remain illuminated?

Go to Step 8

Go to Step 7

7 | Is the vehicle being worked on a Super Chassis w/JE4 and RQ3/U86? | Go to Step 13 | Go to Step 10
8 | Is the vehicle being worked on a Super Chassis w/JE4 and RQ3/U86? | Go to Step 9 | Go to Step 16
9 |

• | Leave the test lamp connected.

• | Disconnect the trailer stop lamps switch.

Does the test lamp remain illuminated?

Go to Step 16

Go to Step 12

10 | Inspect the stop lamps switch for proper adjustment. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes. Did you find and correct the condition? | Go to Step 20 | Go to Step 13
11 | Inspect for poor connections at the stop lamp 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 20 | Go to Step 17
12 | Inspect for poor connections at the harness connector of the trailer stop lamp 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 20 | Go to Step 18
13 | Inspect for poor connections at the harness connector of the stop lamp 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 20 | Go to Step 19
14 | Repair a short to voltage on the rear stop/turn lamp supply voltage circuit between the turn signal switch and the stop lamps. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 20 | --
15 | Repair a short to voltage on the stop lamps supply voltage circuit between the stop lamps relay and the turn signal switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 20 | --
16 | Repair a short to voltage on 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 20 | --
17 | Replace the stop lamps relay. Did you complete the replacement? | Go to Step 20 | --
18 | Replace the trailer stop lamps switch. Refer to Trailer Stop Lamp Switch Replacement in Air Brakes. Did you complete the replacement? | Go to Step 20 | --
19 | Replace the stop lamps switch. Refer to following:

• | Stop Lamp Switch Replacement (Super Chassis w/JE4 and RQ3/U86) in Air Brakes or

• | Stop Lamp Switch Replacement (Others) in Hydraulic Brakes.

Did you complete the replacement?

Go to Step 20

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20 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3