Pinpoint Test B: The Horn Is Always On
Horn
Pinpoint Test B: The Horn Is Always On
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 switched voltage circuits are supplied by the Battery Junction Box (BJB) through circuit 1680 (OG/RD). The horn relay is controlled through circuit 1 (DB) by the horn switch. When the horn switch is pressed, the horn relay control circuit 1 (DB) is grounded through the clockspring to the vehicle harness. The Lighting Control Module (LCM) also supplies a ground to the horn relay through circuit 1 (DB) for the anti-theft function. The LCM supplies a momentary ground to the horn relay through circuit 1 (DB) to indicate the anti-theft system is armed, and an on then off ground when an intrusion is detected. The horn relay is then energized, causing voltage to be applied to circuit 6 (YE/LG), enabling the horn to sound.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Horn relay
- LCM
- Clockspring
- Horn switch (part of the driver air bag module)
- Steering wheel switch harness
PINPOINT TEST B: THE HORN IS ALWAYS ON
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B1 CHECK CIRCUIT 6 (YE/LG) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: Horn Relay.
- Does the horn continue to sound?
Yes
REPAIR the circuit. TEST the system for normal operation.
No
GO to B2.
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B2 CHECK THE HORN RELAY FOR CORRECT OPERATION
- Install a known good relay.
- Does the horn continue to sound?
Yes
REMOVE the known good relay. GO to B3.
No
REMOVE the known good relay. INSTALL a new horn relay. TEST the system for normal operation.
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B3 CHECK THE LCM OPERATION
- Connect: Horn Relay.
- Disconnect: LCM C2145b.
- Does the horn continue to sound?
Yes
GO to B4.
No
GO to B7.
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B4 CHECK CIRCUIT 1 (DB) FOR A SHORT TO GROUND
- Depower the Supplemental Restraint System (SRS). Refer to Air Bag Systems.
- Disconnect: Clockspring C218a.
- Connect: Negative Battery Cable.
- Does the horn continue to sound?
Yes
REPAIR the circuit. REPOWER the SRS. TEST the system for normal operation.
No
GO to B5 .
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B5 CHECK THE CLOCKSPRING
- Connect: Clockspring C218a.
- Remove the driver side air bag module.
- Connect: Negative Battery Cable.
- Disconnect the steering wheel switch harness from the clockspring.
- Does the horn continue to sound?
Yes
INSTALL a new clockspring. TEST the system for normal operation.
No
GO to B6.
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B6 CHECK THE STEERING WHEEL SWITCH HARNESS FOR SHORTS OR DAMAGE
- Visually inspect the steering wheel switch harness for shorts or damage.
- Is the steering wheel switch harness OK?
Yes
INSTALL a new driver side air bag module. TEST the system for normal operation.
No
REPAIR or INSTALL a new steering wheel switch harness. REPOWER the SRS. REFER to Air Bag Systems. TEST the system for normal operation.
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B7 CHECK FOR CORRECT LCM OPERATION
- Disconnect all the LCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the LCM 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 LCM. 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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