Pinpoint Test A: The Horn Is Inoperative
Horn
Pinpoint Tests
Pinpoint Test A: The Horn Is Inoperative
Refer to Wiring Diagram Set 44, Horn/Cigar Lighter for schematic and connector information. Diagrams By Number
Normal Operation
The horn relay control voltage and switched voltage circuits are supplied by the Battery Junction Box (BJB). The horn relay is controlled by the horn switch. When the horn switch is pressed, the horn relay is grounded through the clockspring to the vehicle harness. The horn relay is then energized, causing voltage to be applied to the horn, enabling the horn to sound.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Horn
- Horn relay
- Steering wheel harness
- Clockspring
- Horn switch (part of the driver air bag module and the steering wheel)
PINPOINT TEST A: THE HORN IS INOPERATIVE
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
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A1 CHECK FOR VOLTAGE TO THE HORN RELAY
- Disconnect: Horn Relay.
- Measure the voltage between the horn relay pin 2, circuit 1680 (OG/RD), BJB face side and ground; and between the horn relay pin 3, circuit 1680 (OG/RD), BJB face side and ground.
- Are the voltages greater than 10 volts?
Yes
GO to A2.
No
VERIFY the BJB fuse 10 (20A) is OK. If OK, REPAIR circuit 1680 (OG/RD) for an open. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. Diagrams By Number
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A2 CHECK THE HORN RELAY
- Substitute a known good relay.
- Check the horn.
- Does the horn sound?
Yes
REMOVE the known good relay. INSTALL a new horn relay. TEST the system for normal operation.
No
REMOVE the known good relay. GO to A3.
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A3 CHECK THE HORN RELAY OUTPUT CIRCUITRY
- Connect a fused jumper wire between the horn relay pin 3, circuit 1680 (OG/RD), BJB face side and the horn relay pin 5, circuit 6 (YE/LG), BJB face side.
- Does the horn sound?
Yes
REMOVE the jumper wire. GO to A6.
No
REMOVE the jumper wire. GO to A4.
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A4 CHECK THE HORN VOLTAGE CIRCUIT FOR AN OPEN
- Disconnect: Horn C131.
- Measure the resistance between the horn relay pin 5, circuit 6 (YE/LG), BJB face side, and the horn C131-2, circuit 6 (YE/LG), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to A5.
No
REPAIR circuit 6 (YE/LG) for an open. TEST the system for normal operation.
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A5 CHECK THE HORN GROUND CIRCUIT FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Measure the resistance between the horn C131-1, circuit 57 (BK), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new horn. TEST the system for normal operation.
No
REPAIR circuit 57 (BK) for an open. TEST the system for normal operation.
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A6 CHECK THE CIRCUIT BETWEEN THE HORN RELAY AND THE CLOCKSPRING FOR AN OPEN
- Depower the Supplemental Restraint System (SRS). Refer to Restraint Systems.
- Disconnect: Clockspring C218a.
- Measure the resistance between the horn relay pin 1, circuit 1 (DB), BJB face side, and the clockspring C218a-11, circuit 1 (DB), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to A7.
No
REPAIR circuit 1 (DB) for an open. REPOWER the SRS. REFER to Restraint Systems. TEST the system for normal operation.
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A7 CHECK THE CLOCKSPRING GROUND CIRCUIT FOR AN OPEN
- Measure the resistance between the clockspring C218a-16, circuit 460 (YE/LB), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to A8.
No
REPAIR circuit 460 (YE/LB) for an open. REPOWER the SRS. REFER to Restraint Systems. TEST the system for normal operation.
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A8 CHECK THE CLOCKSPRING FOR AN OPEN
- Remove the driver air bag module. Refer to Restraint Systems.
- Disconnect: Upper Clockspring C218b.
- Measure the resistance between the upper clockspring C218b pin 5, component side, and the clockspring C218a pin 11, component side.
- Measure the resistance between the upper clockspring C218b pin 1, component side, and the clockspring C218a pin 16, component side.
- Are the resistances less than 5 ohms?
Yes
GO to A9.
No
INSTALL a new clockspring and INSTALL the driver air bag module. REFER to Restraint Systems. TEST the system for normal operation.
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A9 CHECK THE STEERING WHEEL HARNESS
- Inspect the steering wheel harness for opens and shorts.
- Is the steering wheel harness OK?
Yes
INSTALL a new driver air bag module or a new steering wheel, as necessary. REFER to Restraint Systems for the driver air bag module, or Steering Column for the steering wheel. TEST the system for normal operation.
No
REPAIR or INSTALL a new steering wheel harness. INSTALL the driver air bag module. REFER to Restraint Systems. TEST the system for normal operation.
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