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 (integrated into 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. The horn relay is then energized, applying voltage to the horn, enabling the horn to sound.
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.
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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
VERIFY the SJB fuse 24 (20A) is OK. If OK, GO to A7. 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 FOR VOLTAGE TO THE CLOCKSPRING
- Ignition OFF.
- Depower the Supplemental Restraint System (SRS). Refer to Supplemental Restraint System Supplemental Restraint System (SRS) Depowering and Repowering.
- 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 THE HORN RELAY COIL GROUND CIRCUIT 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 circuit CRH02 (BU/WH) for an open. REPOWER the SRS. REFER to Supplemental Restraint System Supplemental Restraint System (SRS) Depowering and Repowering. TEST the system for normal operation.
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A4 CHECK FOR VOLTAGE TO THE CLOCKSPRING USING THE CONNECTOR GROUND
- Measure the voltage between the clockspring C218-1, circuit CRH02 (BU/WH), harness side and the clockspring C218-7, circuit GD134 (BK/VT), harness side.
- Is the voltage greater than 10 volts?
Yes
GO to A5.
No
REPAIR circuit GD134 (BK/VT) for an open. INSTALL the driver air bag module. REFER to Supplemental Restraint System Driver Air Bag Module. TEST the system for normal operation.
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A5 CHECK THE CLOCKSPRING FOR AN OPEN
- Remove the driver air bag module. Refer to Supplemental Restraint System Driver Air Bag Module.
- Disconnect: Upper Clockspring Connector.
- 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 A6.
No
INSTALL a new clockspring. REFER to Supplemental Restraint System Service and Repair. 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. REFER to Steering Column Service and Repair. CLEAR the DTCs. REPEAT the self-test.
No
REPAIR or INSTALL a new steering wheel harness. INSTALL the driver air bag module. REFER to Supplemental Restraint System Driver Air Bag Module. TEST the system for normal operation.
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A7 CHECK FOR VOLTAGE TO THE HORN GROUND CIRCUIT
- While pressing the horn switch, measure the voltage between the horn C131-2, circuit CRH04 (VT/GN), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to A8.
No
GO to A9.
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A8 CHECK FOR VOLTAGE TO THE HORN USING THE CONNECTOR GROUND
- 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
REPAIR circuit GD164 (BK/VT) for an open. TEST the system for normal operation.
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A9 CHECK THE SJB HORN OUTPUT CIRCUIT 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 circuit CRH04 (VT/GN) for an open. 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. REFER to Multifunction Electronic Modules Service and Repair. 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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