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 is pressed, the switch closes and ground is applied from the steering wheel harness through the clockspring to the horn relay through circuit CRH02 (BU/WH). The horn relay is then energized, applying voltage to the horn through circuit CRH04 (VT/GN), enabling the horn to sound. Ground for the horn is supplied through circuit GD164 (BK/VT).
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Steering wheel harness
- Horn
- Clockspring
- Horn switch
- 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). Active 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
- Ignition OFF.
- Depower the Supplemental Restraint System (SRS). Refer to Air Bag Systems.
- Disconnect: Clockspring C218.
- Connect: Negative Battery Cable.
- Measure the voltage between the clockspring C218-1, circuit CRH02 (BU/WH), harness side and ground.
- 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 clockspring C218-1, circuit CRH02 (BU/WH), harness side and the SJB C2280b-41, circuit CRH02 (BU/WH), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to A10.
No
REPAIR the circuit. REPOWER the SRS. 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.
- Measure the resistance between the clockspring C218 pin 1, component side and the upper clockspring pin 1, component side.
- Measure the resistance between the clockspring C218 pin 7, component side and the upper clockspring 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 GD134 (BK/VT) FOR AN OPEN
- Measure the resistance between the clockspring C218-7, circuit GD134 (BK/VT), 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 CRH04 (VT/GN) FOR VOLTAGE
- Disconnect: Horn C131.
- While pressing the horn switch, measure the voltage between the horn C131-2, circuit CRH04 (VT/GN), harness side and the horn C131-1, circuit GD164 (BK/VT), 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 A8. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short.
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A8 CHECK CIRCUIT GD164 (BK/VT) FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Measure the resistance between the horn C131-1, circuit GD164 (BK/VT), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to A9.
No
REPAIR the circuit. TEST the system for normal operation.
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A9 CHECK CIRCUIT CRH04 (VT/GN) FOR AN OPEN
- Ignition OFF.
- Disconnect: SJB C2280e.
- Measure the resistance between the SJB C2280e-5, circuit CRH04 (VT/GN), harness side and the horn C131-2, circuit CRH04 (VT/GN), 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.
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