Pinpoint Test B: The Horn Is Always On - Except Stripped Chassis

Horn

Pinpoint Test B: The Horn Is Always On - Except Stripped Chassis

Normal Operation

The Smart Junction Box (SJB) supplies the control and switched voltage to the horn relay (integrated into the SJB (Smart Junction Box)). 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 (Smart Junction Box)). 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 (Smart Junction Box)

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.

B1 CHECK THE SJB (Smart Junction Box) HORN OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE

- Ignition OFF.

- Disconnect: SJB (Smart Junction Box) 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.

B2 CHECK THE HORN SWITCH INPUT

- Disconnect: SJB (Smart Junction Box) C2280B.

- Connect: SJB (Smart Junction Box) C2280E.

Does the horn continue to sound?

Yes
GO to B6.

No
GO to B3.

B3 CHECK THE HORN RELAY COIL GROUND CIRCUIT FOR A SHORT TO GROUND

- Depower the Supplemental Restraint System (SRS). Refer to Restraints and Safety Systems &/or Air Bag Systems.

- 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 (Supplemental Restraint System). REFER to Restraints and Safety Systems &/or Air Bag Systems.
TEST the system for normal operation.

B4 CHECK THE CLOCKSPRING FOR A SHORT TO GROUND

- Remove the driver air bag module.

- Connect: Clockspring C218B.

- Disconnect: Upper Clockspring Connector.

- Measure the resistance between the SJB (Smart Junction Box) 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. TEST the system for normal operation.

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. TEST the system for normal operation.

No
REPAIR or INSTALL a new steering wheel harness. INSTALL the driver air bag module. TEST the system for normal operation.

B6 CHECK FOR CORRECT SJB (Smart Junction Box) OPERATION

- Disconnect all the SJB (Smart Junction Box) connectors.

- Check for:
- corrosion

- damaged pins

- pushed-out pins


- Connect all the SJB (Smart Junction Box) 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 (Smart Junction Box). 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.