Pinpoint Test A: The Horn Is Inoperative
Horn
Pinpoint Tests
Pinpoint Test A: The Horn Is Inoperative
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:
- Fuse
- Wiring, terminals or connectors
- Steering wheel harness
- Horn
- Clockspring
- Driver air bag module
- BCM
- SCCM
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.
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A1 CHECK THE BCM OUTPUT
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: BCM DataLogger .
- Select the active command BCM HORN PID. Command the horn on and then off.
- Does the horn sound when commanded on?
Yes
GO to A2.
No
VERIFY the BCM fuse 22 (20A) is OK. If OK, GO to A9. If not OK, Refer to Wiring Diagrams to identify the possible causes of the circuit short. Diagrams By Number
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A2 CHECK FOR VOLTAGE TO THE SCCM
- Ignition OFF.
- Disconnect: SCCM C2414a .
- Ignition ON.
- Measure the voltage between the SCCM 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.
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A3 CHECK THE HORN RELAY COIL GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: BCM C2280b.
- Measure the resistance between the BCM C2280b-33, circuit CRH04 (VT/GN), harness side and the SCCM 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.
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A4 CHECK THE CLOCKSPRING GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: Clockspring C218a .
- Ignition ON.
- Measure the voltage between the SCCM C2414a-8, circuit CRH04 (VT/GN), harness side and the clockspring C218a-8, circuit GD185 (BK), harness side.
- Is the voltage greater than 10 volts?
Yes
GO to A5.
No
REPAIR circuit GD185 (BK) for an open. TEST the system for normal operation.
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A5 CHECK FOR VOLTAGE TO THE HORN SWITCH CONNECTOR
- Ignition OFF.
- Connect: SCCM C2414a .
- Connect: Clockspring C218a.
- Remove the driver air bag module. Refer to Supplemental Restraint System Driver Air Bag Module.
- Disconnect: Horn Switch C217.
- Ignition ON.
- Measure the voltage between the horn switch C217-A, circuit CRH04 (LB/BK), harness side and the horn switch C217-B, circuit GD185 (GN/TN), harness side.
- Is the voltage greater than 10 volts?
Yes
INSTALL a new driver air bag module. REFER to Supplemental Restraint System Driver Air Bag Module. TEST the system for normal operation.
No
GO to A6.
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A6 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
INSTALL a new steering wheel. REFER to Steering Column Steering Wheel. TEST the system for normal operation.
No
GO to A7.
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A7 CHECK THE CLOCKSPRING FOR AN OPEN
- 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. REFER to Supplemental Restraint System Service and Repair. TEST the system for normal operation.
No
GO to A8.
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A8 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 A13.
No
INSTALL a new clockspring. REFER to Supplemental Restraint System Service and Repair. TEST the system for normal operation.
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A9 CHECK FOR VOLTAGE TO THE HORN
- Ignition OFF.
- Disconnect: Horn C131.
- 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 ground.
- Is the voltage greater than 10 volts?
Yes
GO to A10.
No
GO to A11.
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A10 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 GD124 (BK/VT), 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 GD124 (BK/VT) for an open. TEST the system for normal operation.
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A11 CHECK THE BCM HORN OUTPUT CIRCUIT FOR AN OPEN
- Disconnect: BCM C2280e.
- Measure the resistance between the BCM 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 A12.
No
REPAIR circuit SRH01 (YE/RD) for an open. TEST the system for normal operation.
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A12 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 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. TEST the system for normal operation.
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A13 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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