Pinpoint Test A: The Horn Is Inoperative
Horn
Pinpoint Tests
Pinpoint Test A: The Horn Is Inoperative
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 horn switch (part of the steering wheel) is pressed, the switch is grounded through circuit GD114 (BK/BU). Ground is then supplied to the horn relay coil through circuit CRH02 (BU/WH), energizing the horn relay. The horn relay then sends voltage to the horn through circuit SRH01 (YE/RD), enabling the horn to sound. Ground for the horn is supplied through circuit GD123 (BK/GY).
Possible Causes
- Fuse
- Wiring, terminals or connectors
- Horn
- Clockspring
- Steering wheel harness
- Horn switch (part of the steering wheel)
- SJB
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. Refer to Battery.
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A1 CHECK THE SJB OUTPUT
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: SJB DataLogger.
- Select the SJB 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.
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A2 CHECK CIRCUIT CRH02 (BU/WH) FOR VOLTAGE
- Depower the Supplemental Restraint System (SRS). Refer to Air Bag Systems.
- Disconnect: Clockspring C218.
- Measure the voltage between the clockspring C218-8, circuit CRH02 (BU/WH), harness side and ground.
- Connect: Negative Battery Cable.
- Is the voltage greater than 10 volts?
Yes
GO to A4.
No
GO to A3.
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A3 CHECK CIRCUIT CRH02 (BU/WH) FOR AN OPEN
- Disconnect: SJB C2280b.
- Measure the resistance between the SJB C2280b-41, circuit CRH02 (BU/WH) harness side, and the clockspring C218-8, circuit CRH02 (BU/WH), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to A10.
No
REPAIR the circuit. REPOWER the SRS. REFER to Air Bag Systems. TEST the system for normal operation.
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A4 CHECK THE CLOCKSPRING FOR AN OPEN
- Remove the driver air bag module.
- Disconnect: Upper Clockspring Connector.
- Measure the resistance between the clockspring C218 pin 8, component side and the upper clockspring connector pin 1 component side.
- Measure the resistance between the clockspring C218 pin 5, component side and the upper clockspring connector pin 4, component side.
- Is the resistance less than 5 ohms?
Yes
GO to A5.
No
INSTALL a new clockspring. TEST the system for normal operation.
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A5 CHECK CIRCUIT GD114 (BK/BU) FOR AN OPEN
- Measure the resistance between the clockspring C218-5, circuit GD114 (BK/BU), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to A6.
No
REPAIR the circuit. INSTALL the driver air bag module. TEST the system for normal operation.
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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. INSTALL the driver air bag module. TEST the system for normal operation.
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A7 CHECK CIRCUIT GD123 (BK/GY) FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Disconnect: Horn C131.
- Measure the resistance between the horn C131-1, circuit GD123 (BK/GY), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to A8.
No
REPAIR the circuit. TEST the system for normal operation.
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A8 CHECK CIRCUIT SRH01 (YE/RD) FOR VOLTAGE
- Connect: Negative Battery Cable.
- 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 GD123 (BK/GY), harness side.
- Is the voltage greater than 10 volts?
Yes
INSTALL a new horn. REFER to Horn Service and Repair. TEST the system for normal operation.
No
VERIFY the SJB 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.
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A9 CHECK CIRCUIT SRH01 (YE/RD) FOR AN OPEN
- Disconnect: SJB C2280e.
- Measure the resistance between the SJB 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 the circuit. TEST the system for normal operation.
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A10 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. 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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