Schematic Reference: Exterior Lights Schematics

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

Go to Step 2

Go to Symptoms - Lighting Systems

1. Probe the tractor/trailer receptacle's left turn signal circuit with a test lamp that is connected to a good ground.
2. Place the turn signal lever in the LEFT turn position.
3. Probe the tractor/trailer receptacle's right turn signal circuit with a test lamp that is connected to a good ground.
4. Place the turn signal lever in the RIGHT turn position.

Does the test lamp illuminate and flash with both the left and right sides?

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

Go to Step 3

Do the vehicles turn signals operate properly?

Go to Step 4

Go to Symptoms - Lighting Systems

1. Place the turn signal lever in the OFF position.
2. Disconnect the turn trailer relay of the inoperative side.
3. Probe the turn trailer relay's coil side control circuit with a test lamp that is connected to a good ground.
4. Place the turn signal lever in the turn position of the inoperative side.

Does the test lamp illuminate and flash?

Go to Step 5

Go to Step 10

Connect a test lamp between the turn trailer relay's coil side control circuit and the coil side ground circuit.

Does the test lamp illuminate and flash?

Go to Step 6

Go to Step 11

Probe the switch side voltage supply circuit of the turn trailer 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

1. Connect a fused jumper wire between the turn trailer relay's switch side voltage supply circuit and the switch side output circuit.
2. Probe the inoperative turn signal circuit of the tractor/trailer receptacle with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 8

Does the fuse in the jumper wire open?

Go to Step 13

Go to Step 14

Inspect for poor connections at the appropriate turn trailer 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

Repair an open or short to ground in the turn trailer relay's coil side control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 16

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Repair an open in the turn trailer relay's coil side ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 16

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Repair an open or short to ground in the turn trailer relay's switch side voltage supply circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 16

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Repair a short to ground in the tractor/trailer receptacle turn signal voltage supply circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 16

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Repair an open in the tractor/trailer receptacle turn signal voltage supply circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 16

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Replace the appropriate turn trailer relay.

Did you complete the replacement?

Go to Step 16

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Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3