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 and switched voltage is supplied by the Battery Junction Box (BJB) through circuit 1680 (OG/RD). The horn relay is controlled through circuit 1 (DB) by the horn switch. When the horn switch is pressed, the horn relay control circuit 1 (DB) is grounded through the clockspring and circuit 460 (YE/LB). The horn relay is then energized, which causes voltage to be applied to circuit 6 (YE/LG), enabling the horn to sound. Ground to the horn is supplied through circuit 57 (BK).
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Horn
- Horn relay
- Steering wheel switch 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.
NOTE: Failure to disconnect the battery when instructed will result in false resistance readings. Refer to Battery.
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A1 CHECK CIRCUIT 1680 (OG/RD) FOR VOLTAGE
- 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.
- Is the voltage greater than 10 volts?
Yes
GO to A2.
No
VERIFY the BJB fuse 10 (20A) is OK. If OK, REPAIR the circuit. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short.
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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 CIRCUIT 6 (YE/LG) 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 the circuit. TEST the system for normal operation.
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A5 CHECK THE HORN GROUND CIRCUIT 57 (BK) 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 the circuit. TEST the system for normal operation.
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A6 CHECK CIRCUIT 1 (DB) BETWEEN THE HORN RELAY AND THE CLOCKSPRING FOR AN OPEN
- Depower the Supplemental Restraint System (SRS). Refer to Air Bag 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 the circuit. TEST the system for normal operation.
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A7 CHECK CIRCUIT 460 (YE/LB) 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 the circuit. TEST the system for normal operation.
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A8 CHECK THE CLOCKSPRING
- Remove the driver air bag module.
- 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. TEST the system for normal operation.
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A9 CHECK THE STEERING WHEEL SWITCH HARNESS
- Inspect the steering wheel switch harness for opens and shorts.
- Is the steering wheel switch harness OK?
Yes
INSTALL a new driver air bag module or a new steering wheel, as necessary. TEST the system for normal operation.
No
REPAIR or INSTALL a new steering wheel switch harness. INSTALL the driver air bag module. TEST the system for normal operation.
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