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 switches (part of the steering wheel) are pressed, the switches are grounded to the steering wheel through circuit GD165 (BK), and the clockspring to the instrument panel cross-car beam through circuit GD116 (BK/VT). Ground is then supplied to the horn relay through circuit CRH02 (BU/WH), energizing the horn relay. The horn relay then sends voltage to the horn through circuit CRH04 (VT/GN), enabling the horn to sound. Ground for the horn is supplied through circuit GD123 (BK/GY).
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Horn
- Clockspring
- Steering wheel harness
- Horn switches (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.
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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 A8. If not OK, REFER to the Wiring Diagrams to identify the possible causes of circuit short.
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A2 CHECK THE CLOCKSPRING GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Depower the Supplemental Restraint System (SRS). REFER to Air Bag Systems.
- Disconnect: Clockspring C218a.
- Measure the resistance between the clockspring C218a-7, 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. REFER to Air Bag Systems. TEST the system for normal operation.
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A3 CHECK FOR VOLTAGE TO THE CLOCKSPRING
- Connect: Negative Battery Cable.
- Measure the voltage between the clockspring C218a-8, circuit CRH02 (BU/WH), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to A5.
No
GO to A4.
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A4 CHECK THE HORN RELAY COIL GROUND CONTROL CIRCUIT FOR AN OPEN
- Disconnect: SJB C2280b.
- Measure the resistance between the SJB C2280b-41, circuit CRH02 (BU/WH), harness side and the clockspring C218a-8, circuit CRH02 (BU/WH), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to A11.
No
REPAIR circuit CRH02 (BU/WH) for an open. REPOWER the SRS. REFER to Air Bag Systems. TEST the system for normal operation.
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A5 CHECK THE STEERING WHEEL HARNESS GROUND CIRCUIT FOR AN OPEN
- Remove the driver air bag module.
- Disconnect: Upper Clockspring C218b.
- Measure the resistance between the upper clockspring C218b-2, circuit GD165 (BK), harness side and a metal point on the steering wheel.
- Is the resistance less than 5 ohms?
Yes
GO to A6.
No
REPAIR circuit GD165 (BK) for an open. INSTALL the driver air bag module. TEST the system for normal operation.
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A6 CHECK THE STEERING WHEEL HARNESS FOR AN OPEN
- Disconnect: Horn Switch C2996 and C2997.
- Measure the resistance between the upper clockspring C218b-1, circuit CRH02 (BU/WH), harness side and the horn switch C2996-1, circuit CRH02 (BU/WH), harness side; and between the upper clockspring C218b-1, circuit CRH02 (BU/WH), harness side and the horn switch C2997-1, circuit CRH02 (BU/WH), harness side.
- Are the resistances less than 5 ohms?
Yes
GO to A7.
No
REPAIR circuit CRH02 (BU/WH) for an open. INSTALL the driver air bag module. TEST the system for normal operation.
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A7 CHECK THE CLOCKSPRING FOR AN OPEN
- Measure the resistance between the clockspring C218a pin 7, component side and the clockspring C218b pin 2, component side.
- Measure the resistance between the clockspring C218a pin 8, component side and the clockspring C218b 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.
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A8 CHECK FOR VOLTAGE TO THE HORN
- Disconnect: Horn C131.
- 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 A9.
No
GO to A10.
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A9 CHECK FOR VOLTAGE TO THE HORN USING THE CONNECTOR GROUND
- 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 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
REPAIR circuit GD123 (BK/GY) for an open. TEST the system for normal operation.
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A10 CHECK THE HORN VOLTAGE SUPPLY CIRCUIT FOR AN OPEN
- 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 A11.
No
REPAIR circuit CRH04 (VT/GN) for an open. TEST the system for normal operation.
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A11 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. REPOWER the SRS. REFER to 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. REFER to Air Bag Systems.
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