Pinpoint Test B: The Horn Is Always On
Horn
Pinpoint Tests
Pinpoint Test B: The Horn Is Always On
Refer to Wiring Diagram Set 44, Horn/Cigar Lighter for schematic and connector information. Diagrams By Number
Normal Operation
The horn relay is controlled through circuit 1 (DB) by the horn switch and through the Lighting Control Module (LCM). When the horn switch is pressed, the horn relay control circuit 1 (DB) is grounded through the clockspring to the vehicle harness. The horn relay is then energized, which causes voltage to be applied to circuit 6 (YE/LG), enabling the horn to sound.
When the LCM has enabled the anti-theft system, the LCM supplies a ground through the horn relay control circuit 1 (DB). The horn relay is then energized, which causes voltage to be applied to circuit 6 (YE/LG), enabling the horn to sound.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Horn relay
- LCM
- Clockspring
- Horn switch (part of the driver air bag module and the steering wheel)
- Steering wheel switch harness
PINPOINT TEST B: THE HORN IS ALWAYS ON
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B1 CHECK THE HORN CIRCUIT
- Ignition OFF.
- Disconnect: Horn Relay.
- Does the horn continue to sound?
Yes
REPAIR circuit 6 (YE/LG). TEST the system for normal operation.
No
GO to B2.
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B2 CHECK THE HORN RELAY
- Substitute a known good relay.
- 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 B3.
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B3 CHECK THE LCM
- Connect: Horn Relay.
- Disconnect: LCM C2145b.
- Does the horn continue to sound?
Yes
GO to B4.
No
GO to B7.
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B4 CHECK CIRCUIT 1 (DB) FOR A SHORT TO GROUND
- Disconnect: Clockspring C218a.
- Does the horn continue to sound?
Yes
REPAIR the circuit. TEST the system for normal operation.
No
GO to B5.
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B5 CHECK THE CLOCKSPRING
- Connect: Clockspring C218a.
- Connect: Negative Battery Cable.
- Remove the driver air bag module.
- Disconnect: Clockspring C218b.
- Does the horn continue to sound?
Yes
INSTALL a new clockspring. TEST the system for normal operation.
No
GO to B6.
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B6 CHECK THE STEERING WHEEL SWITCH HARNESS
- Visually inspect the steering wheel switch harness for shorts or damage.
- 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
INSTALL a new steering wheel switch harness. INSTALL the driver air bag module. TEST the system for normal operation.
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B7 CHECK THE LCM FOR CORRECT OPERATION
- Disconnect all the LCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the LCM connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new LCM. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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