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

Go to Step 2

Go to Symptoms - Lighting Systems

1. Ensure the brake pedal is not being pressed down.
2. Probe the upfitter connector's stop lamp supply voltage circuit with a test lamp that is connected to a good ground.

Does the test lamp remain OFF?

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

Go to Step 3

1. Leave the test lamp connected.
2. Disconnect the stop lamp switch connector C1.

Does the test lamp illuminate?

Go to Step 6

Go to Step 4

If the vehicle being worked on has hydraulic brakes, check the adjustment of the stop lamp switch. Refer to Stop Lamp Switch Adjustment in Hydraulic Brakes.

Did you find and correct the condition?

Go to Step 8

Go to Step 5

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 8

Go to Step 7

Repair a short to voltage in the upfitter connector's stop lamp supply voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 8

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Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes or Stop Lamp Switch Replacement in Air Brakes.

Did you complete the replacement?

Go to Step 8

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Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3