For 1990-2009 cars

### Test Description

The number below refers to the step number on the diagnostic table.

1. The horn requires the highest current while sounding. If the resistance in the horn control circuit or ground circuit is higher than 0.5 ohm, malfunction may occur. Inspect the circuit for current troubles.

Step | Action | Yes | No
--- | --- | --- | ---
DEFINITION: The diagnostic procedure is used to diagnose the one horn trouble condition in several horn systems.
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Press the horn switch. Do all the horns sound? | Go to Testing for Electrical Intermittents | Go to Step 3
3 |

1. Disconnect the inoperative horn.
2. Connect a test lamp between the horn control circuit and the good ground.
3. Press and hold the horn button.

Does the test light illuminate?

Go to Step 4

Go to Step 7

4 |

1. Connect a test lamp between the control circuit and the horn ground circuit.
2. Press and hold the horn button.

Does the test light illuminate?

Go to Step 5

Go to Step 6

5 | Inspect for poor connection of the inoperative horn. Refer to Testing for Intermittent Conditions and Poor Connections. Does the test light illuminate? | Go to Step 11 | Go to Step 6
6 |

1. Connect a 15A fused jumper between the battery positive terminal and the horn control terminal.
2. Connect another jumper between the battery negative terminal and the horn ground terminal.

Does the horn sound?

Go to Step 9

Go to Step 10

7 | Repair poor connection in horn control circuit. Refer to Circuit Testing and Wiring Repairs. Is the repair complete? | Go to Step 11 | --
8 | Repair open circuit or poor connection in horn ground circuit. Refer to Circuit Testing and Wiring Repairs. Is the repair complete? | Go to Step 11 | --
9 | Repair the high resistance in the horn control circuit or horn ground circuit. Resistance as low as 0.5 ohm can cause trouble to the horn. Refer to Circuit Testing and Wiring Repairs. Is the repair complete? | Go to Step 11 | --
10 | Replace the inoperative horn. Did you complete the replacement? | Go to Step 11 | --
11 | Operate the horn. Is the horn working normally? | System OK | Go to Step 1