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Test Description

WARNING: This page is about a different car, the 2004 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 5:  Tests for voltage at the battery positive voltage terminal of the horn relay coil.
  2. 7:  Tests for voltage at the battery positive voltage terminal of the horn relay switch. The HORN fuse supplies power to the battery positive voltage terminal of the horn relay switch.
  3. 15:  The horns need maximum current flow to operate properly. A high resistance (greater than 0.5 ohms) in the horn control circuit or the horn ground circuit could cause operating problems with the horns. Inspect the circuits for faults that would restrict current flow.
Horns Inoperative

Step Action Yes No
1 Did you perform the Horns Diagnostic System Check? Go to Step 2  Go to Diagnostic System Check - Horns 
2 Did you review the Horns operation and perform the necessary inspections? Go to Step 3  Go to Symptoms - Horns 
3 Depress the horn switch.
Do the horns operate?		 Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems Go to Step 4 
4
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the horn relay ON and OFF.
Does the horn relay turn ON and OFF with each command?		 Go to Step 12  Go to Step 5 
5 
  1. Disconnect the horn relay.
  2. Connect a test lamp between the battery positive voltage circuit of the horn relay coil and a good ground.
Does the test lamp illuminate?		 Go to Step 6  Go to Step 16 
6
  1. Connect a test lamp between the battery positive voltage circuit of the horn relay coil and the horn relay control circuit.
  2. Depress and hold the horn switch.
Does the test lamp illuminate?		 Go to Step 7  Go to Step 13 
7  Connect a test lamp between the battery positive voltage circuit of the horn relay switch and a good ground.
Does the test lamp illuminate?		 Go to Step 8  Go to Step 17 
8 Momentarily connect a 15-amp fused jumper wire between the battery positive voltage circuit of the horn relay switch and the horn control circuit.
Do the horns operate?		 Go to Step 11  Go to Step 9 
9
  1. Reconnect the horn relay.
  2. Disconnect the horn connector.
  3. Connect a test lamp between the horn control circuit and a good ground.
  4. Depress and hold the horn switch.
Does the test lamp illuminate?		 Go to Step 10  Go to Step 18 
10
  1. Connect a test lamp between the horn control circuit and the horn ground circuit.
  2. Depress and hold the horn switch.
Does the test lamp illuminate?		 Go to Step 14  Go to Step 19 
11 Inspect for poor connections at the horn 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 23  Go to Step 20 
12 Test the horn switch signal for a short to voltage or open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 23  Go to Step 22 
13 Test the control circuit of the horn relay for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 23  Go to Step 22 
14
  1. Connect a 15-amp fused jumper wire between the positive battery terminal and the control terminal of the horn.
  2. Momentarily connect another jumper wire between the negative battery terminal and the ground terminal of the horn.
Does the horn sound?		 Go to Step 15  Go to Step 21 
15  Repair the high resistance in the horn control circuit or the horn ground (A resistance as low as 0.5Ω could cause operating problems with the horns). Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 23  -
16 Repair the open or high resistance in the battery positive voltage circuit of the horn relay coil. Refer to Circuit Testing andWiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 23  -
17 Repair the open or high resistance in the battery positive voltage circuit of the horn relay switch. Refer to Circuit Testing andWiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 23  -
18 Repair the open or high resistance in the horn control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 23  -
19 Repair the open or high resistance in the horn ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 23  -
20 Replace the horn relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems.
Did you complete the replacement?		 Go to Step 23  -
21 Replace the horn assembly. Refer to Horn Replacement .
Did you complete the replacement?		 Go to Step 23  -
22 Replace the Body Control Module (BCM). Refer to Body Control Module Replacement in Body Control Systems.
Did you complete the replacement?		 Go to Step 23  -
23 Operate the horns.
Do the horns operate properly?		 System OK Go to Step 1 
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