Pinpoint Test B: The Horn Is Always On

Horn

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 part of the driver air bag module) is closed and ground is routed through the clockspring to the horn relay, energizing the horn relay. The Battery Junction Box (BJB) supplies the switched and control voltage to the horn relay, which is integrated into the Body Control Module (BCM). The horn relay then provides voltage to the horn, enabling the horn to sound. If incorrectly installed, the horn pad can cause the horn switch to be closed at all times.

The Tire Pressure Monitor (TPM)/Vehicle Security Module (VSM) is also wired to the horn relay coil controlled circuit. The TPM/VSM sounds the horn during TPMS sensor training.

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors
- Steering wheel harness
- Clockspring
- Driver air bag module
- BCM
- TPM/VSM

PINPOINT TEST B: THE HORN IS ALWAYS ON

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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B1 CHECK THE HORN SWITCH INPUT TO THE BCM

- Ignition OFF.
- Disconnect: BCM C2280E.
- Disconnect: BCM C2280D.
- Ignition ON.
- Does the horn continue to sound?

Yes
GO to B2.

No
GO to B3.

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B2 CHECK THE HORN CIRCUIT FOR SHORT TO VOLTAGE

- Ignition OFF.
- Disconnect: BCM C2280A.
- Ignition ON.
- Does the horn continue to sound?

Yes
REPAIR circuit CHR04 (VT/GN) for a short to voltage. TEST the system for normal operation.

No
GO to B7.

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B3 CHECK THE TPM/VSM

- Ignition OFF.
- Connect: BCM C2280E.
- Connect: BCM C2280D.
- Disconnect: TPM/ VSM C4321B.
- Does the horn continue to sound?

Yes
GO to B4.

No
GO to B8.

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B4 CHECK THE HORN SWITCH INPUT CIRCUIT FOR A SHORT TO GROUND

- Disconnect: Clockspring C218B.
- Does the horn continue to sound?

Yes
REPAIR circuit CRH03 (BN) for a short to ground. TEST the system for normal operation.

No
GO to B5.

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B5 CHECK HORN SWITCH

- Connect: Clockspring C218B.
- Remove the driver air bag module. Refer to Supplemental Restraint System Driver Air Bag Module.
- Disconnect: Horn Switch C217A.
- Does the horn continue to sound?

Yes
GO to B6.

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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B6 CHECK THE CLOCKSPRING FOR A SHORT TO GROUND

- Disconnect: Clockspring C218C.
- Does the horn continue to sound?

Yes
INSTALL a new clockspring. REFER to Supplemental Restraint System Service and Repair. TEST the system for normal operation.

No
The steering wheel harness has a short circuit. INSTALL a new steering wheel. REFER to Steering Column Removal and Replacement. TEST the system for normal operation.

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B7 CHECK FOR CORRECT BCM 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 Body Control Module (BCM). 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 TPM/VSM OPERATION

- Disconnect all the TPM/ VSM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the TPM/ VSM 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 TPM module. REFER to Wheels and Tires 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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