Pinpoint Test B: The Horn Is Always On
Horn
Pinpoint Tests
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 and switched voltage is supplied by the Bussed Electrical Center (BEC) through fuse 46 (25A). The Smart Junction Box (SJB) receives the horn signal through circuit 1 (DB) from the horn switch (part of the steering wheel). When the horn switch is pressed, ground is supplied through the clockspring to the vehicle harness through circuit 1205 (BK). The SJB then activates the horn relay through circuit 1323 (OG/RD). Voltage is then sent to the horn through circuit 6 (YE/LG), enabling the horns to sound. Ground is provided to the horns through circuit 1205 (BK).
- DTC B1897 (Horn Switch Circuit Failure) - an on-demand DTC that sets when the SJB detects a short to ground on circuit 1323 (OG/RD) and circuit 1 (DB).
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Horn switch (part of the steering wheel)
- Clockspring
- Horn relay
- BEC
- SJB
PINPOINT TEST B: THE HORN IS ALWAYS ON
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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B1 RETRIEVE THE SJB DTCs
- Check the recorded results from the SJB on-demand self-test.
- Is DTC B1897 retrieved?
Yes
GO to B2.
No
GO to B8.
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B2 CHECK FOR A SHORT TO GROUND INSIDE THE BEC
- Ignition OFF.
- Disconnect: BEC C1035a.
- Does the horn continue to sound?
Yes
INSTALL a new BEC. TEST the system for normal operation.
No
GO to B3.
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B3 CHECK CIRCUIT 1323 (OG/RD) FOR A SHORT TO GROUND
- Disconnect: SJB C2280c.
- Connect: BEC C1035a.
- Does the horn continue to sound?
Yes
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
No
GO to B4.
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B4 CHECK THE SJB
- Connect: SJB C2280c.
- Disconnect: SJB C2280b.
- Does the horn continue to sound?
Yes
GO to B10.
No
GO to B5.
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B5 CHECK CIRCUIT 1 (DB) FOR A SHORT TO GROUND
- Depower the Supplemental Restraint System (SRS). Refer to Air Bag Systems.
- Disconnect: Clockspring C2274.
- Measure the resistance between the SJB C2280b-39, circuit 1 (DB), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to B6.
No
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
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B6 CHECK THE CLOCKSPRING FOR A SHORT TO GROUND
- Connect: Clockspring C2274.
- Connect: SJB C2280b.
- Remove the driver air bag module.
- Disconnect: Upper Clockspring Connector.
- Disconnect: Negative Battery Cable.
- Does the horn continue to sound?
Yes
INSTALL a new clockspring. CLEAR the DTCs. REPEAT the self-test.
No
GO to B7.
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B7 CHECK THE HORN SWITCH FOR A SHORT TO GROUND
- Connect: Upper Clockspring Connector.
- Does the horn continue to sound?
Yes
REPAIR or INSTALL a new steering wheel harness. CLEAR the DTCs. REPEAT the self-test.
No
INSTALL a new steering wheel. INSTALL the driver air bag module. CLEAR the DTCs. REPEAT the self-test.
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B8 CHECK THE HORN RELAY FOR CORRECT OPERATION
- Disconnect: Horn Relay .
- Install a known good relay.
- Does the horn continue to sound?
Yes
REMOVE the known good relay. INSTALL a new horn relay. TEST the system for normal operation.
No
REMOVE the known good relay. GO to B9.
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B9 CHECK CIRCUIT 6 (YE/LG) FOR A SHORT TO VOLTAGE
- Disconnect: BEC C1035c.
- Does the horn continue to sound?
Yes
REPAIR the circuit. TEST the system for normal operation.
No
INSTALL a new BEC. TEST the system for normal operation.
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B10 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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