Pinpoint Test A: The Horn Is Inoperative
Horn
Pinpoint Test A: The Horn Is Inoperative
Normal Operation
The Smart Junction Box (SJB) supplies the switched and control voltage to the horn relay (integrated into the SJB (Smart Junction Box)). When the horn switch (part of the steering wheel) is pressed, ground is supplied to the horn relay, energizing the horn relay. The horn relay then sends voltage to the horn, enabling the horn to sound.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Horn
- Clockspring
- Steering wheel harness
- Horn switch (part of the steering wheel)
- SJB (Smart Junction Box)
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.
A1 CHECK THE SJB (Smart Junction Box) OUTPUT
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: SJB (Smart Junction Box) DataLogger.
- Select the SJB (Smart Junction Box) horn PID (HORN). Command the horn on and then off.
Does the horn sound when commanded on?
Yes
GO to A2.
No
GO to A7.
A2 CHECK FOR VOLTAGE TO THE CLOCKSPRING
- Ignition OFF.
- Depower the Supplemental Restraint System (SRS). Refer to Restraints and Safety Systems &/or Air Bag Systems.
- Disconnect: Clockspring C218A.
- Connect: Negative Battery Cable.
- Measure the voltage between the clockspring C218A-8, circuit CRH02 (BU/WH), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to A4.
No
GO to A3.
A3 CHECK THE HORN RELAY COIL GROUND CIRCUIT FOR AN OPEN
- Disconnect: SJB (Smart Junction Box) C2280B.
- Measure the resistance between the SJB (Smart Junction Box) C2280B-41, circuit CRH02 (BU/WH), harness side, and the clockspring C218A-8, circuit CRH02 (BU/WH), harness side.
Is the resistance less than 5 ohms?
Yes
GO to A10.
No
REPAIR circuit CRH02 (BU/WH) for an open. REPOWER the SRS (Supplemental Restraint System). REFER to Restraints and Safety Systems &/or Air Bag Systems. TEST the system for normal operation.
A4 CHECK THE CLOCKSPRING FOR AN OPEN
- Remove the driver air bag module.
- Disconnect: Upper Clockspring Connector.
- Measure the resistance between the clockspring C218a pin 8, component side and the upper clockspring connector pin 1, component side.
- Measure the resistance between the clockspring C218a pin 5, component side and the upper clockspring connector pin 4, component side.
Are both resistances less than 5 ohms?
Yes
GO to A5.
No
INSTALL a new clockspring. INSTALL the driver air bag module. TEST the system for normal operation.
A5 CHECK THE CLOCKSPRING GROUND CIRCUIT FOR AN OPEN
- Measure the resistance between the clockspring C218A-5, circuit GD116 (BK/VT), harness side and ground.
Is the resistance less than 5 ohms?
Yes
GO to A6.
No
REPAIR circuit GD116 (BK/VT) for an open. REPOWER the SRS (Supplemental Restraint System). REFER to Restraints and Safety Systems &/or Air Bag Systems. TEST the system for normal operation.
A6 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 steering wheel. CLEAR the DTCs. REPEAT the self-test.
No
REPAIR or INSTALL a new steering wheel harness. TEST the system for normal operation.
A7 CHECK FOR VOLTAGE TO THE HORN GROUND CIRCUIT
- Ignition OFF.
- Disconnect: Horn C131.
- While pressing the driver air bag 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 A8.
No
VERIFY the SJB (Smart Junction Box) fuse 24 (20A) is OK. If OK, GO to A9. If not OK, Refer to the Wiring Diagrams to identify the possible causes of the circuit short. Electrical Diagrams
A8 CHECK FOR VOLTAGE TO THE HORN USING THE CONNECTOR GROUND
- While pressing the driver air bag against the steering wheel, measure the voltage between the horn C131-2, circuit SRH01 (YE/RD), harness side, and the horn C131-1, circuit GD123 (BK/GY), harness side.
Is the voltage greater than 10 volts?
Yes
INSTALL a new horn. REFER to Horn . TEST the system for normal operation.
No
REPAIR circuit GD123 (BK/GY) for an open. TEST the system for normal operation.
A9 CHECK THE SJB (Smart Junction Box) HORN OUTPUT CIRCUIT FOR AN OPEN
- Disconnect: SJB (Smart Junction Box) C2280E.
- Measure the resistance between the SJB (Smart Junction Box) C2280E-5, 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 A10.
No
REPAIR circuit SRH01 (YE/RD) for an open. TEST the system for normal operation.
A10 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. TEST the system for normal operation.