GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

Connector End View Reference: Master Electrical Component List in Wiring Systems

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 inoperative rear trailer stop/turn lamp supply voltage circuit of the trailer tow connector with a test lamp that is connected to a good ground.
  2. Place the turn signal switch in the TURN position of the inoperative side.

Does the test lamp illuminate and flash?

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

Go to Step 3

3

Do the vehicle's turn signals operate properly?

Go to Step 4

Go to Turn Signal Lamps and/or Indicators Inoperative

4

  1. Disconnect the appropriate turn trailer relay.
  2. Probe the turn signal lamp supply voltage circuit of the turn trailer relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate and flash?

Go to Step 5

Go to Step 9

5

Connect a test lamp between the turn signal lamp supply voltage circuit of the turn trailer relay and the ground circuit.

Does the test lamp illuminate and flash?

Go to Step 6

Go to Step 10

6

Probe the battery positive voltage 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 11

7

  1. Install a 20 amp fused jumper wire between the battery positive voltage circuit of the turn trailer relay and the trailer stop/turn lamp supply voltage circuit.
  2. Probe the stop/turn lamp supply voltage circuit of the trailer tow connector with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 8

Go to Step 12

8

Inspect for poor connections at the 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 14

Go to Step 13

9

Repair an open, high resistance or short to ground in the turn signal lamp supply voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 14

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10

Repair an open or high resistance in the ground circuit of the turn trailer relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 14

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11

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

Did you complete the repair?

Go to Step 14

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12

Repair an open, high resistance or short to ground in the stop/turn lamp supply voltage circuit of the turn trailer relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 14

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13

Replace the turn trailer relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 14

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14

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2