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

When the driver air bag module is pressed, the normally open horn switch (which is integrated into the driver air bag module) is closed and ground is routed through the clockspring and the Steering Column Control Module (SCCM) to the horn relay, energizing the horn relay. The Body Control Module (BCM) supplies the switched and control voltage to the horn relay, which is integrated into the BCM. The horn relay then provides voltage to the horn, enabling the horn to sound.

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors
- Steering wheel harness
- Clockspring
- Driver air bag module
- BCM
- SCCM

PINPOINT TEST B: THE HORN IS ALWAYS ON

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B1 CHECK THE BCM HORN OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE

- Ignition OFF.
- Disconnect: BCM C2280e .
- Does the horn continue to sound?

Yes
REPAIR circuit SRH01 (YE/RD) for a short to voltage. TEST the system for normal operation.

No
GO to B2.

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B2 CHECK THE HORN SWITCH INPUT TO THE BCM

- Connect: BCM C2280e .
- Disconnect: BCM C2280b .
- Does the horn continue to sound?

Yes
GO to B7.

No
GO to B3.

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B3 CHECK THE HORN SWITCH INPUT FOR A SHORT TO GROUND

- Connect: BCM C2280b.
- Disconnect: SCCM C2414a.
- Does the horn continue to sound?

Yes
REPAIR circuit CRH04 (VT/GN) for a short to ground. TEST the system for normal operation.

No
GO to B4.

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B4 CHECK THE HORN SWITCH

- Connect: SCCM C2414a.
- Remove the driver air bag module. Refer to Supplemental Restraint System Driver Air Bag Module.
- Does the horn continue to sound?

Yes
GO to B5.

No
INSTALL a new driver air bag module. REFER to Supplemental Restraint System Driver Air Bag Module. TEST the system for normal operation.

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B5 CHECK THE STEERING WHEEL HARNESS

- Disconnect: Clockspring C218b.
- Does the horn continue to sound?

Yes
GO to B7.

No
INSTALL a new steering wheel. REFER to Steering Column Steering Wheel. TEST the system for normal operation.

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B6 CHECK THE CLOCKSPRING FOR A SHORT TO GROUND

- Remove the clockspring. Refer to Supplemental Restraint System Service and Repair.
- Does the horn continue to sound?

Yes
GO to B8.

No
INSTALL a new clockspring. REFER to Supplemental Restraint System Service and Repair. TEST the system for normal operation.

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B7 CHECK FOR CORRECT TBCM OPERATION

- Disconnect all the BCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the BCM 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 BCM. REFER to Multifunction Electronic Modules Service and Repair. 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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B8 CHECK FOR CORRECT SCCM OPERATION

- Disconnect all the SCCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the SCCM 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 SCCM. REFER to Steering Column Switches Service and Repair. 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. RUN the on-demand self-test (required to clear certain DTCs). CORRECT any unresolved DTCs. CLEAR all DTCs. TEST the system for normal operation.

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