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
The Smart Junction Box (SJB) supplies the switched and control voltage to the horn relay (part of the SJB). When the horn switch is pressed, the switch closes and ground is applied from the steering wheel harness through the clockspring to the horn relay. The horn relay is then energized, applying 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
- Horn switch
- SJB
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.
NOTE: Failure to disconnect the battery when instructed will result in false resistance readings. Refer to Battery.
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A1 CHECK THE SJB OUTPUT
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: SJB DataLogger.
- Select the SJB PID (HORN). Active command the horn on and then off.
- Does the horn sound when commanded on?
Yes
GO to A2.
No
GO to A8.
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A2 CHECK FOR VOLTAGE TO THE CLOCKSPRING
- Ignition OFF.
- Depower the Supplemental Restraint System (SRS). Refer to Restraint Systems.
- Disconnect: Clockspring C218a.
- Connect: Negative Battery Cable.
- Measure the voltage between the clockspring C218a-8, circuit SRH01 (YE/RD), 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 CONTROL CIRCUIT FOR AN OPEN
- Disconnect: SJB C2280b.
- Measure the resistance between the SJB C2280b-41, circuit SRH01 (YE/RD), harness side and the clockspring C218a-8, 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. REPOWER the SRS. REFER to Restraint Systems. TEST the system for normal operation.
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A4 CHECK THE STEERING WHEEL HARNESS GROUND CIRCUIT FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Measure the resistance between the clockspring C218a-5, circuit GD133 (BK), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to A5.
No
REPAIR circuit GD133 (BK) for an open. REPOWER the SRS. REFER to Restraint Systems. TEST the system for normal operation.
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A5 CHECK THE CLOCKSPRING FOR AN OPEN
- Remove the driver air bag module. Refer to Restraint Systems.
- Disconnect: Clockspring C218b.
- Measure the resistance between the clockspring C218a pin 8, component side and the clockspring C218b pin 1, component side.
- Is the resistance less than 5 ohms?
Yes
GO to A6.
No
INSTALL a new clockspring. REFER to Restraint Systems. TEST the system for normal operation.
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A6 CHECK THE CLOCKSPRING GROUND CIRCUIT FOR AN OPEN
- Measure the resistance between the clockspring C218a pin 5, component side and the clockspring C218b pin 4, component side.
- Is the resistance less than 5 ohms?
Yes
GO to A7.
No
INSTALL a new clockspring. REFER to Restraint Systems. TEST the system for normal operation.
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A7 CHECK THE STEERING WHEEL HARNESS FOR DAMAGE OR OPENS
- Inspect the steering wheel harness for damage or opens.
- Is the steering wheel harness OK?
Yes
INSTALL a new driver air bag module. REFER to Restraint Systems. TEST the system for normal operation.
No
REPAIR or INSTALL a new steering wheel harness. INSTALL the driver air bag module. REFER to Restraint Systems. TEST the system for normal operation.
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A8 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 CRH02 (BU/WH), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to A9.
No
VERIFY the SJB fuse 24 (20A) is OK. If OK, GO to A10. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. Diagrams By Number
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A9 CHECK FOR VOLTAGE TO THE HORN USING THE CONNECTOR GROUND
- While pressing the horn switch, measure the voltage between the horn C131-2, circuit CRH02 (BU/WH), harness side and the horn C131-1, circuit GD120 (BK/GN), 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 GD120 (BK/GN) for an open. TEST the system for normal operation.
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A10 CHECK THE SJB HORN OUTPUT CIRCUIT FOR AN OPEN
- Disconnect: SJB C2280e.
- Measure the resistance between the SJB C2280e-5, circuit CRH02 (BU/WH), harness side and the horn C131-2, circuit CRH02 (BU/WH), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to A11.
No
REPAIR circuit CRH02 (BU/WH) for an open. TEST the system for normal operation.
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A11 CHECK FOR CORRECT SJB OPERATION
- Disconnect all the SJB connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the SJB 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 SJB. REFER to Body Control Systems. 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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