Pinpoint Test A: The Horn Is Inoperative
Horn
Pinpoint Test
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 horn relay control voltage and the horn relay switched voltage circuits are supplied by the Smart Junction Box (SJB) fuse 13 (15A). The horn relay (integrated into the SJB) is controlled through the clockspring to the horn switch (part of the steering wheel). When the horn switch is pressed, the horn relay control circuit grounds through the clockspring. The horn relay is then energized, enabling the horn to sound.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Horn
- Clockspring
- 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 FOR VOLTAGE TO THE HORN
- Ignition OFF.
- Disconnect: Horn C131.
- Measure the voltage between the horn C131-1, circuit CRH02 (BU/WH), harness side and ground with the horn switch pressed.
- Is the voltage greater than 10 volts?
Yes
GO to A2.
No
VERIFY the SJB fuse 13 (15A) is OK. If OK, GO to A3. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. Diagrams By Number
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A2 CHECK THE HORN GROUND CIRCUIT FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Measure the resistance between the horn C131-2, circuit GD123 (BK/GY), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new horn. REFER to Horn Service and Repair. TEST the system for normal operation.
No
REPAIR circuit GD123 (BK/GY) for an open. TEST the system for normal operation.
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A3 BYPASS THE SJB
- Connect: Horn C131.
- Disconnect: SJB C2280a.
- Connect a fused jumper wire between the SJB C2280a-30, circuit CRH02 (BU/WH), harness side and between the SJB C2280a-32, circuit SBB05 (GY/RD), harness side.
- Does the horn sound?
Yes
REMOVE the jumper wire. GO to A4.
No
REMOVE the jumper wire. REPAIR circuit CRH02 (BU/WH) for an open. TEST the system for normal operation.
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A4 CHECK THE HORN REQUEST INPUT CIRCUIT AT THE SJB FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Disconnect: SJB C2280d.
- Measure the resistance between the SJB C2280d-12, circuit SRH01 (YE/RD), harness side and ground while pressing the horn switch.
- Is the resistance less than 5 ohms with the switch pressed?
Yes
GO to A8.
No
GO to A5.
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A5 CHECK THE HORN REQUEST INPUT CIRCUIT FOR AN OPEN
- Disconnect: Clockspring C218a.
- Measure the resistance between the clockspring C218a-2, circuit SRH01 (YE/RD), harness side and the SJB C2280d-12, circuit SRH01 (YE/RD), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to A6.
No
REPAIR circuit SRH01 (YE/RD) for an open. TEST the system for normal operation.
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A6 CHECK THE CLOCKSPRING GROUND CIRCUIT FOR AN OPEN
- Measure the resistance between the clockspring C218a-5, circuit GD174 (BK/WH), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to A7.
No
REPAIR circuit GD174 (BK/WH) for an open. TEST the system for normal operation.
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A7 CHECK THE CLOCKSPRING FOR AN OPEN
- Disconnect: Upper Clockspring C218c.
- Remove the driver air bag module. Refer to Restraint Systems.
- Measure the resistance between the clockspring C218c pin 1, component side and the upper clockspring C218a pin 5, component side.
- Measure the resistance between the clockspring C218c pin 5, component side and the upper clockspring C218a pin 2, component side.
- Are the resistances less than 5 ohms?
Yes
INSTALL a new steering wheel. REFER to Steering Column. INSTALL the driver air bag module. REFER to Restraint Systems. TEST the system for normal operation.
No
INSTALL a new clockspring. REFER to Restraint Systems. TEST the system for normal operation.
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A8 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 Body Control 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.
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