Pinpoint Test B: The Horn Is Always On - Except Stripped Chassis
Horn
Pinpoint Tests
Pinpoint Test B: The Horn Is Always On - Except Stripped Chassis
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 control and switched voltage to the horn relay (integrated into the SJB). When the driver air bag is pressed, the horn switch (part of the driver air bag module) supplies ground through the clockspring to the horn relay coil (integrated into the SJB). The horn relay is then energized routing voltage to the horn, enabling the horn to sound.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Clockspring
- Steering wheel harness
- Horn switch (part of the driver air bag module)
- SJB
PINPOINT TEST B: THE HORN IS ALWAYS ON - EXCEPT STRIPPED CHASSIS
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 B6.
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 Supplemental Restraint System Supplemental Restraint System (SRS) Depowering and Repowering.
- Disconnect: Clockspring C218b.
- Measure the resistance between the clockspring C218b-5, 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 Supplemental Restraint System Supplemental Restraint System (SRS) Depowering and Repowering. 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 Supplemental Restraint System Driver Air Bag Module.
- Connect: Clockspring C218b.
- Disconnect: Upper Clockspring Connector.
- 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 Supplemental Restraint System Service and Repair. TEST the system for normal operation.
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B5 CHECK THE STEERING WHEEL HARNESS
- Inspect the steering wheel harness for damage or shorts.
- Is the steering wheel harness OK?
Yes
INSTALL a new driver air bag module. REFER to Supplemental Restraint System Driver Air Bag Module. TEST the system for normal operation.
No
REPAIR or INSTALL a new steering wheel harness. INSTALL the driver air bag module. REFER to Supplemental Restraint System Driver Air Bag Module. TEST the system for normal operation.
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B6 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 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.
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