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. Probe the tractor/trailer receptacle stop lamps voltage supply circuit with a test lamp that is connected to a good ground.
2. Press down the brake pedal.

Does the test lamp illuminate?

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

Go to Step 3

3 | Do the vehicle's stop lamps illuminate? | Go to Step 4 | Go to Stop Lamps Inoperative
4 |

1. Disconnect the trailer stop relay.
2. Probe the stop lamp switch signal circuit of the trailer stop 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 5

Go to Step 10

5 |

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

Does the test lamp illuminate?

Go to Step 6

Go to Step 11

6 | Probe the battery positive voltage circuit of the trailer stop relay with a test lamp that is connected to a good ground. Does the test lamp illuminate? | Go to Step 7 | Go to Step 12
7 |

1. Connect a 50 amp fused jumper wire between the battery positive voltage circuit of the trailer stop relay and the stop lamp supply voltage of the trailer stop relay.
2. Probe the tractor/trailer receptacle stop lamp supply voltage circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 8

8 | Does the fuse in the jumper wire open? | Go to Step 13 | Go to Step 14
9 | Inspect for poor connections at the trailer stop 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 16 | Go to Step 15
10 | Repair an open, high resistance, or short to ground in the stop lamp switch signal circuit of the trailer stop relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 16 | --
11 | Repair an open or high resistance in the trailer stop relay coil side ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 16 | --
12 | Repair an open, high resistance, or short to ground in the battery positive voltage circuit of the trailer stop relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 16 | --
13 | Repair a short to ground in the tractor/trailer receptacle stop lamps supply voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 16 | --
14 | Repair an open or high resistance in the tractor/trailer receptacle stop lamps supply voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 16 | --
15 | Replace the trailer stop relay. Did you complete the replacement? | Go to Step 16 | --
16 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3