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 Central Junction Box (CJB) supplies the switched and control voltage to the horn relay (part of the Generic Electronic Module (GEM)). 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
- Driver air bag module
- GEM
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 FOR VOLTAGE TO THE HORN
- Ignition OFF.
- Disconnect: Horn C131.
- While pressing the horn switch, measure the voltage between the horn C131-1, circuit 29-GJ6 (OG/YE), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to A2.
No
GO to A3.
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A2 CHECK FOR VOLTAGE TO THE HORN USING THE CONNECTOR GROUND
- While pressing the horn switch, measure the voltage between the horn C131-1, circuit 29-GJ6 (OG/YE), harness side and the horn C131-2, circuit 31-GJ6 (BK), 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 31-GJ6 (BK) for an open. TEST the system for normal operation.
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A3 CHECK FOR VOLTAGE TO THE GEM
- Connect: Horn C131.
- Disconnect: GEM C201c.
- Measure the voltage between the GEM C201c-4, circuit 29-GJ8 (OG), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to A4.
No
VERIFY the CJB fuse 136 (15A) is OK. If OK, REPAIR circuit 29-GJ8 (OG) for an open. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. TEST the system for normal operation. Diagrams By Number
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A4 BYPASS THE GEM
- Connect a fused jumper wire between the GEM C201c-4, circuit 29-GJ8 (OG), harness side and the GEM C201c-3, circuit 29-GJ6 (OG/YE), harness side.
- Does the horn sound?
Yes
REMOVE the jumper wire. GO to A5.
No
REMOVE the jumper wire. REPAIR circuit 29-GJ6 (OG/YE) for an open. TEST the system for normal operation.
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A5 CHECK FOR VOLTAGE TO THE CLOCKSPRING
- Depower the Supplemental Restraint System (SRS). Refer to Restraint Systems.
- Connect: GEM C201c.
- Connect: Negative Battery Cable.
- Disconnect: C218 .
- Measure the voltage between the clockspring C218-6, circuit 31S-GJ5 (BK/BU), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to A7.
No
GO to A6.
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A6 CHECK HORN RELAY COIL GROUND CONTROL CIRCUIT FOR AN OPEN
- Disconnect: GEM C201b.
- Measure the resistance between the clockspring C218-6, circuit 31-GJ5 (BK/BU), harness side and the GEM C201b-15, circuit 31S-GJ7 (BK/BU), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to A10.
No
REPAIR the horn relay coil ground controlled circuit for an open. TEST the system for normal operation.
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A7 CHECK FOR VOLTAGE TO THE CLOCKSPRING USING THE CONNECTOR GROUND
- Measure the voltage between the clockspring C218-6, circuit 31S-GJ5 (BK/BU), harness side and the clockspring C218-7, circuit 91-PG30 (BK/WH), harness side.
- Is the voltage greater than 10 volts?
Yes
GO to A8.
No
REPAIR circuit 91-PG30 (BK/WH) for an open. TEST the system for normal operation.
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A8 CHECK THE HORN CONTACT BAR FOR DAMAGE
- Remove the driver air bag module. Refer to Restraint Systems.
- Inspect the horn contact bar for damage.
- Is the horn contact bar OK?
Yes
GO to A9.
No
INSTALL a new driver air bag module. REFER to Restraint Systems. TEST the system for normal operation.
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A9 CHECK 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 clockspring. REFER to Restraint Systems. TEST the system for normal operation.
No
REPAIR or INSTALL a new steering wheel harness. INSTALL the driver air bag module. REFER to Restraint Systems. TEST the system for normal operation.
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A10 CHECK FOR CORRECT GEM OPERATION
- Disconnect all the GEM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the GEM 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 GEM. REFER to Body Control 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.
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