Pinpoint Test B: The Horn Is Always On
Horn
Pinpoint Tests
Pinpoint Test B: The Horn Is Always On
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 driver air bag is pressed against the steering wheel, ground is supplied to the horn relay coil, energizing the horn relay. The horn relay then provides voltage to the horn, enabling the horn to sound.
The horn switch is not a single component, but consists of the contact points located on the steering wheel and driver air bag module. One set of contacts is part of the steering wheel itself and the other set is part of a metal plate mounted to the rear of the driver air bag module. Springs mounted to the metal plate are isolated by plastic seats on the steering wheel. When the driver air bag module is pressed against the steering wheel, the contacts on the driver air bag module and the steering wheel touch to complete the circuit.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Clockspring
- Steering wheel harness
- Steering wheel
- Driver air bag module
- SJB
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.
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B1 CHECK THE SJB HORN OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: SJB C2280e.
- Does the horn continue to sound?
Yes
REPAIR circuit SRH01 (YE/RD) for a short to voltage. TEST the system for normal operation.
No
GO to B2.
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B2 CHECK THE HORN SWITCH INPUT
- Disconnect: SJB C2280b.
- Connect: SJB C2280e.
- Does the horn continue to sound?
Yes
GO to B7.
No
GO to B3.
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B3 CHECK THE HORN RELAY COIL GROUND CIRCUIT FOR A SHORT TO GROUND
- Depower the Supplemental Restraint System (SRS). Refer to Restraint Systems.
- Disconnect: Clockspring C218a.
- Measure the resistance between the clockspring C218a-1, circuit CRH02 (BU/WH), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to B4.
No
REPAIR circuit CRH02 (BU/WH) for a short to ground. REPOWER the SRS. REFER to Restraint Systems. TEST the system for normal operation.
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B4 CHECK THE CLOCKSPRING FOR A SHORT TO GROUND
- Remove the driver air bag module. Refer to Restraint Systems.
- Disconnect: Upper Clockspring Connector.
- Connect: Clockspring C218a.
- Measure the resistance between the SJB C2280b-41, circuit CRH02 (BU/WH), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to B5.
No
INSTALL a new clockspring. REFER to Restraint Systems. TEST the system for normal operation.
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B5 CHECK THE STEERING WHEEL HARNESS FOR DAMAGE OR SHORTS
- Inspect the steering wheel harness for damage or shorts.
- Is the steering wheel harness OK?
Yes
GO to B6.
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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B6 CHECK THE SPRING SEATS ON THE STEERING WHEEL
- Inspect the spring seats on the steering wheel for damage.
- Are the spring seats OK?
Yes
INSTALL a new driver air bag module. REFER to Restraint Systems. TEST the system for normal operation.
No
INSTALL a new steering wheel. REFER to Steering Column. TEST the system for normal operation.
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B7 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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