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 horn relay control and switched voltage is supplied by the Bussed Electrical Center (BEC) through fuse 46 (25A). The 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 horn through circuit 1205 (BK).
- DTC B1217 (Horn Relay Coil Circuit Failure) - a continuous and on-demand DTC that sets when the SJB detects a short to voltage on circuit 1323 (OG/RD) or circuit 1 (DB).
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Horn relay
- Horn switch (part of the steering wheel)
- Horn
- Clockspring
- BEC
- 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 HORN CONTROL COMMAND
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: SJB DataLogger.
- Select the SJB horn PID (HORN), and command the horn on.
- Does the horn sound?
Yes
GO to A10.
No
GO to A2.
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A2 CHECK THE SJB
- Ignition OFF.
- Disconnect: SJB C2280c.
- Connect a fused jumper wire between the SJB C2280c-29, circuit 1323 (OG/RD), harness side and ground.
- Does the horn sound?
Yes
REMOVE the jumper wire. GO to A14.
No
LEAVE the jumper wire connected. GO to A3.
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A3 CHECK THE HORN RELAY FOR CORRECT OPERATION
- Disconnect: Horn Relay .
- Install a known good relay.
- Does the horn sound?
Yes
REMOVE the known good relay and the jumper wire. INSTALL a new horn relay. TEST the system for normal operation.
No
REMOVE the known good relay. GO to A4.
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A4 CHECK THE HORN RELAY CONTROL FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Disconnect: Horn Relay.
- Measure the resistance between the horn relay pin 85, harness side and ground.
- Is the resistance less than 5 ohms?
Yes
REMOVE the jumper wire. GO to A6.
No
REMOVE the jumper wire. GO to A5.
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A5 CHECK CIRCUIT 1323 (OG/RD) FOR AN OPEN
- Disconnect: BEC C1035a.
- Measure the resistance between the SJB C2280c-29, circuit 1323 (OG/RD), harness side and the BEC C1035a-A1, circuit 1323 (OG/RD), harness side.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new BEC. TEST the system for normal operation.
No
REPAIR the circuit. TEST the system for normal operation.
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A6 CHECK THE VOLTAGE SUPPLY TO THE HORN RELAY
- Connect: Negative Battery Cable.
- Ignition ON.
- Measure the voltage between the horn relay pin 86, harness side and ground; and between the horn relay pin 87, harness side and ground.
- Are the voltages greater than 10 volts?
Yes
GO to A7.
No
VERIFY the BEC fuse 46 (25A) is OK. If OK, INSTALL a new BEC. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short.
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A7 CHECK CIRCUIT 6 (YE/LG) FOR AN OPEN
- Ignition OFF.
- Disconnect: BEC C1035c.
- Disconnect: Horn C131.
- Measure the resistance between the horn C131-2, circuit 6 (YE/LG), harness side and the BEC C1035c-D4, circuit 6 (YE/LG), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to A8.
No
REPAIR the circuit. TEST the system for normal operation.
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A8 CHECK CIRCUIT 1205 (BK) FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Measure the resistance between the horn C131-1, circuit 1205 (BK), 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 THE BEC FOR AN INTERNAL OPEN
- Connect: Negative Battery Cable.
- Connect: BEC C1035c.
- Connect a fused jumper wire between the horn relay pin 30, harness side and the horn relay pin 87, harness side.
- Measure the voltage between the horn C131-2, circuit 6 (YE/LG), harness side and ground.
- 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
INSTALL a new BEC. TEST the system for normal operation.
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A10 CHECK THE HORN SIGNAL TO THE SJB
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Disconnect: SJB C2280b.
- Measure the resistance between the SJB C2280b-39, circuit 1 (DB), harness side and ground, while pressing and releasing the horn switch.
- Is the resistance less than 5 ohms with the horn switch pressed, and greater than 10,000 ohms with the horn switch released?
Yes
GO to A14.
No
GO to A11.
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A11 CHECK CIRCUIT 1 (DB) FOR AN OPEN
- 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 the clockspring C2274-7, circuit 1 (DB), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to A12.
No
REPAIR the circuit. REPOWER the SRS. REFER to Air Bag Systems. TEST the system for normal operation.
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A12 CHECK THE CLOCKSPRING FOR AN OPEN
- Remove the driver side air bag module.
- Disconnect: Upper Clockspring Connector.
- Measure the resistance between the clockspring C2274 pin 7, component side and the upper clockspring connector pin 5, component side.
- Measure the resistance between the clockspring C2274 pin 6, component side and the upper clockspring connector pin 4, component side.
- Are the resistances less than 5 ohms?
Yes
GO to A13.
No
INSTALL a new clockspring. TEST the system for normal operation.
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A13 CHECK THE HORN SWITCH FOR CORRECT OPERATION
- Measure the resistance between the upper clockspring connector pin 5, circuit 1 (BK), harness side and the upper clockspring connector pin 4, circuit 1205 (GN), harness side, while pressing and releasing the horn switch.
- Is the resistance less than 5 ohms with the horn switch pressed, and greater than 10,000 ohms with the horn switch released?
Yes
REPAIR circuit 1205 (BK) between the clockspring and ground. INSTALL the driver air bag module. TEST the system for normal operation.
No
INSTALL a new steering wheel. INSTALL the driver air bag module. TEST the system for normal operation.
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A14 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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