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 Electrical Diagrams.
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 (Tire Pressure Monitor) /VSM (Vehicle Security Module) sounds the horn during TPMS (Tire Pressure Monitoring System) sensor training.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Steering wheel harness
- Clockspring
- Driver air bag module
- BCM (Body Control Module)
- TPM (Tire Pressure Monitor) /VSM (Vehicle Security Module)
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.
B1 CHECK THE HORN SWITCH INPUT TO THE BCM (Body Control Module)
- Ignition OFF.
- Disconnect: BCM (Body Control Module) C2280E.
- Disconnect: BCM (Body Control Module) C2280D.
- Ignition ON.
Does the horn continue to sound?
Yes
GO to B2.
No
GO to B3.
B2 CHECK THE HORN CIRCUIT FOR SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: BCM (Body Control Module) 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.
B3 CHECK THE TPM (Tire Pressure Monitor) /VSM (Vehicle Security Module)
- Ignition OFF.
- Connect: BCM (Body Control Module) C2280E.
- Connect: BCM (Body Control Module) C2280D.
- Disconnect: TPM (Tire Pressure Monitor) /VSM (Vehicle Security Module) C4321B.
- Ignition ON.
Does the horn continue to sound?
Yes
GO to B4.
No
GO to B8.
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.
B5 CHECK HORN SWITCH
- Connect: Clockspring C218B.
- Remove the 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. TEST the system for normal operation.
B6 CHECK THE CLOCKSPRING FOR A SHORT TO GROUND
- Disconnect: Clockspring C218C.
Does the horn continue to sound?
Yes
INSTALL a new clockspring. TEST the system for normal operation.
No
The steering wheel harness has a short circuit. INSTALL a new steering wheel. TEST the system for normal operation.
B7 CHECK FOR CORRECT BCM (Body Control Module) OPERATION
- Disconnect all the BCM (Body Control Module) connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the BCM (Body Control Module) 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 (Body Control Module). 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.
B8 CHECK FOR CORRECT TPM (Tire Pressure Monitor) /VSM (Vehicle Security Module) OPERATION
- Disconnect all the TPM (Tire Pressure Monitor) /VSM (Vehicle Security Module) connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the TPM (Tire Pressure Monitor) /VSM (Vehicle Security Module) 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 (Tire Pressure Monitor) module. 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.