Pinpoint Test A: The Horn Is Inoperative
Horn
Pinpoint Test A: The Horn Is Inoperative
Refer to Wiring Diagram Set 44, Horn/Cigar Lighter for schematic and connector information [1][2]Diagrams By Number.
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, the switch is grounded to the steering wheel. Ground is then 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.
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). Active command the horn on and then off.
Does the horn sound when commanded on?
Yes
GO to A2.
No
VERIFY the SJB (Smart Junction Box) fuse 24 (20A) is OK. If OK, GO to A7. If not OK, REFER to the Wiring Diagrams to identify the possible causes of circuit short [1][2]Diagrams By Number.
A2 CHECK THE CLOCKSPRING GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Depower the Supplemental Restraint System (SRS). Refer to Restraints and Safety Systems &/or Air Bag Systems.
- Disconnect: Clockspring C2274.
- Measure the resistance between the clockspring C2274-5, circuit GD116 (BK/VT), harness side and ground.
Is the resistance less than 5 ohms?
Yes
GO to A3.
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.
A3 CHECK FOR VOLTAGE TO THE CLOCKSPRING
- Connect: Negative Battery Cable.
- Measure the voltage between the clockspring C2274-8, circuit CRH02 (BU/WH), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to A5.
No
GO to A4.
A4 CHECK THE HORN RELAY COIL GROUND CONTROL 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 C2274-8, 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.
A5 CHECK THE STEERING WHEEL HARNESS FOR OPENS
- Remove the driver air bag module.
- Disconnect: Upper Clockspring.
- Inspect the steering wheel harness for opens.
Is the steering wheel harness OK?
Yes
GO to A6.
No
REPAIR or INSTALL a new steering wheel harness. INSTALL the driver air bag module. TEST the system for normal operation.
A6 CHECK THE CLOCKSPRING FOR AN OPEN
- Measure the resistance between the clockspring C2274 pin 5, component side and the upper clockspring pin 2, component side.
- Measure the resistance between the clockspring C2274 pin 8, component side and the upper clockspring pin 1, component side.
Are the resistances less than 5 ohms?
Yes
INSTALL a new steering wheel. TEST the system for normal operation.
No
INSTALL a new clockspring. TEST the system for normal operation.
A7 CHECK FOR VOLTAGE TO THE HORN
- Disconnect: Horn C131.
- While pressing the horn switch, 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
GO to A9.
A8 CHECK FOR VOLTAGE TO THE HORN USING THE CONNECTOR GROUND
- While pressing the horn switch, measure the voltage between the horn C131-2, circuit SRH01 (YE/RD), harness side and the horn C131-1, circuit GD129 (BK/YE), 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 GD129 (BK/YE) for an open. TEST the system for normal operation.
A9 CHECK THE HORN VOLTAGE SUPPLY 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). REPOWER the SRS (Supplemental Restraint System). REFER to Restraints and Safety Systems &/or Air Bag 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. REPOWER the SRS (Supplemental Restraint System). REFER to Restraints and Safety Systems &/or Air Bag Systems.