Pinpoint Test A: The Horn Is Inoperative

Horn

Pinpoint Test A: The Horn Is Inoperative

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.

This pinpoint test is intended to diagnose the following:

- Fuse

- Wiring, terminals or connectors

- Steering wheel harness

- Horn

- Clockspring

- Driver air bag module

- BCM (Body Control Module)

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.

A1 CHECK FOR VOLTAGE TO THE HORN

- Ignition OFF.

- Disconnect: Horn C131.

- While pressing the horn switch, measure the voltage between the horn C131-2, circuit CRH04 (VT/GN), harness side and ground.





Is the voltage greater than 10 volts?

Yes
GO to A2.

No
GO to A3.

A2 CHECK FOR VOLTAGE TO THE HORN USING THE CONNECTOR GROUND

- While pressing the horn switch, measure the voltage between the horn C131-2, circuit CRH04 (VT/GN), harness side and the horn C131-1, circuit GD123 (BK/GY), harness side.





Is the voltage greater than 10 volts?

Yes
INSTALL a new horn. REFER to Horn Service and Repair. TEST the system for normal operation.

No
REPAIR circuit GD123 (BK/GY) for an open. TEST the system for normal operation.

A3 CHECK FOR VOLTAGE TO THE BCM (Body Control Module)

- Connect: Horn C131.

- Disconnect: BCM (Body Control Module) C2280A.

- Measure the voltage between the BCM (Body Control Module) C2280A-2, circuit SBB26 (YE/RD), harness side and ground.





Is the voltage greater than 10 volts?

Yes
GO to A4.

No
VERIFY the BJB (Battery Junction Box) fuse 26 (20A) is OK. If OK, REPAIR circuit SBB26 (YE/RD) for an open. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short Electrical Diagrams. TEST the system for normal operation.

A4 BYPASS THE BCM (Body Control Module)

- Connect a fused jumper wire between the BCM (Body Control Module) C2280A-2, circuit SBB26 (YE/RD), harness side and the BCM (Body Control Module) C2280A-3, circuit CRH04 (VT/GN), harness side.





Does the horn sound?

Yes
REMOVE the jumper wire. GO to A5.

No
REMOVE the jumper wire. REPAIR circuit CRH04 (VT/GN) for an open. TEST the system for normal operation.

A5 CHECK FOR VOLTAGE TO THE CLOCKSPRING

- Connect: BCM (Body Control Module) C2280A.

- Disconnect: Clockspring C218B.

- Measure the voltage between the clockspring C218B-11, circuit CRH03 (BN), harness side and ground.





Is the voltage greater than 10 volts?

Yes
GO to A7.

No
GO to A6.

A6 CHECK HORN RELAY COIL GROUND CONTROL CIRCUIT FOR AN OPEN

- Disconnect: BCM (Body Control Module) C2280E.

- Measure the resistance between the clockspring C218B-11, circuit CRH03 (BN), harness side and the BCM (Body Control Module) C2280E-21, circuit CRH03 (BN), harness side.





Is the resistance less than 5 ohms?

Yes
GO to A10.

No
REPAIR circuit CRH03 (BN) for an open. TEST the system for normal operation.

A7 CHECK FOR VOLTAGE TO THE CLOCKSPRING USING THE CONNECTOR GROUND

- Measure the voltage between the clockspring C218B-11, circuit CRH03 (BN), harness side and the clockspring C218B-15, circuit GD116 (BK/VT), harness side.





Is the voltage greater than 10 volts?

Yes
GO to A8.

No
REPAIR circuit GD116 (BK/VT) for an open. TEST the system for normal operation.

A8 CHECK FOR VOLTAGE TO THE HORN SWITCH CONNECTOR

- Connect: BCM (Body Control Module) C2280E.

- Connect: Clockspring C218B.

- Remove the driver air bag module.

- Disconnect: Horn Switch C217A.

- Disconnect: Horn Switch C217B.

- Measure the voltage between the horn switch C217A-1, circuit (RD), harness side and the horn switch C217B-1, circuit (VT), harness side.





Is the voltage greater than 10 volts?

Yes
INSTALL a new driver air bag module. TEST the system for normal operation.

No
GO to A9.

A9 CHECK FOR VOLTAGE TO THE CLOCKSPRING

- Disconnect: Clockspring C218C.

- Measure the voltage between the clockspring connector C218C pin 4, component side and the clockspring C218C pin 8 component side.





Is the voltage greater than 10 volts?

Yes
The steering wheel harness has an open circuit. INSTALL a new steering wheel. TEST the system for normal operation.

No
INSTALL a new clockspring. TEST the system for normal operation.

A10 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.