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 (part of the steering wheel) is closed and a path to ground is routed through the clockspring and the Steering Column Control Module (SCCM) and the horn relay is energized. The Body Control Module (BCM) supplies the switched and control voltage to the horn relay, which is integrated into the BCM (Body Control Module). 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
- Horn
- Clockspring
- Steering wheel harness
- Horn switch (part of the steering wheel)
- BCM (Body Control Module)
- SCCM (Steering Column 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 THE BCM (Body Control Module) OUTPUT
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: BCM (Body Control Module) DataLogger.
- Select the active command BCM (Body Control Module) HORN PID. Command the horn on and then off.
Does the horn sound when commanded on?
Yes
GO to A2.
No
VERIFY the BCM (Body Control Module) fuse 22 (20A) is OK. If OK, GO to A8. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short Electrical Diagrams.
A2 CHECK FOR VOLTAGE TO THE SCCM (Steering Column Control Module)
- Ignition OFF.
- Disconnect: SCCM (Steering Column Control Module) C2414A.
- Ignition ON.
- Measure the voltage between the SCCM (Steering Column Control Module) C2414A-8, circuit CRH04 (VT/GN), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to A4.
No
GO to A3.
A3 CHECK THE HORN RELAY COIL GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: BCM (Body Control Module) C2280B.
- Measure the resistance between the BCM (Body Control Module) C2280B-33, circuit CRH04 (VT/GN), harness side and the SCCM (Steering Column Control Module) C2414A-8, circuit CRH04 (VT/GN), harness side.
Is the resistance less than 5 ohms?
Yes
GO to A12.
No
REPAIR circuit CRH04 (VT/GN) for an open. TEST the system for normal operation.
A4 CHECK THE CLOCKSPRING GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Connect: Negative Battery Cable.
- Disconnect: Clockspring C218A.
- Ignition ON.
- Measure the voltage between the SCCM (Steering Column Control Module) C2414A-8, circuit CRH04 (VT/GN), harness side and the clockspring C218A-8, circuit GD115 (BK/GY), harness side.
Is the voltage greater than 10 volts?
Yes
GO to A5.
No
REPAIR circuit GD115 (BK/GY) for an open. TEST the system for normal operation.
A5 CHECK FOR VOLTAGE TO THE CLOCKSPRING
- Ignition OFF.
- Disconnect: Clockspring C218B.
- Ignition ON.
- Measure the voltage between the clockspring connector C218B pin 4, component side and the clockspring C218B pin 10, 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
GO to A6.
A6 CHECK THE FOR VOLTAGE AT THE CLOCKSPRING
- Measure the voltage between the clockspring connector C218B pin 4, component side and ground.
Is the voltage greater than 10 volts?
Yes
INSTALL a new clockspring. TEST the system for normal operation.
No
GO to A7.
A7 CHECK FOR AN OPEN IN THE CLOCKSPRING
- Remove the clockspring.
- Measure the resistance between the clockspring connector C218B pin 4, component side and the clockspring connector C218C pin 1, component side
Is the resistance less than 5 ohms?
Yes
GO to A12.
No
INSTALL a new clockspring. TEST the system for normal operation.
A8 CHECK FOR VOLTAGE TO THE HORN
- Disconnect: Horn C131.
- While pressing the horn switch, measure the voltage between the horn C131-2, circuit SRH01 (YE/RD), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to A9.
No
GO to A10.
A9 CHECK THE HORN GROUND CIRCUIT FOR CONTINUITY
- While pressing the driver airbag module against the steering wheel, measure the voltage between the horn C131-2, circuit SRH01 (YE/RD), 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 . TEST the system for normal operation.
No
REPAIR circuit GD123 (BK/GY) for an open. TEST the system for normal operation.
A10 CHECK THE BCM (Body Control Module) HORN OUTPUT CIRCUIT FOR AN OPEN
- Disconnect: BCM (Body Control Module) C2280E.
- Measure the resistance between the BCM (Body Control Module) C2280E-3, circuit SRH01 (YE/RD), harness side, and the horn C131-2, circuit SRH01 (YE/RD), harness side.
Is the resistance less than 5 ohms?
Yes
GO to A11.
No
REPAIR circuit SRH01 (YE/RD) for an open. TEST the system for normal operation.
A11 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. TEST the system for normal operation.
A12 CHECK FOR CORRECT SCCM (Steering Column Control Module) OPERATION
- Disconnect all the SCCM (Steering Column Control Module) connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the SCCM (Steering Column 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 SCCM (Steering Column 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. RUN the on-demand self-test (required to clear certain DTCs). CORRECT any unresolved DTCs. CLEAR all DTCs. TEST the system for normal operation.