• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Horn Relay Control | 1 | 1 | B2750 00 | -- |
Horn PCB Relay Control | 2 | 2 | B2750 00 | -- |
Left Horn Control | 1 | 1 | 1 | -- |
Right Horn Control | 2 | 2 | 2 | -- |
Horn Switch Ground | -- | 1,2 | 1,2 | -- |
Left Horn Ground | -- | 2 | 2 | -- |
Right Horn Ground | -- | 1 | 1 | -- |
1. Left horn malfunction 2. Right horn malfunction |
Battery positive voltage is applied at all times to the horn relay coil and the horn relay switch. Pressing the horn switch applies ground through the switch contacts and the horn relay control circuit to the coil side of the relay, energizing the relay. Battery voltage is then applied through the switch side of the relay, the horn fuse, and the horn control circuit to the horns. The body control module (BCM) may also apply ground to the horn relay control circuit as described above. The horns sound as long as ground is applied to the horn relay control circuit.
A short to ground in the horn relay control circuit or a short to voltage in the horn control circuit will cause the horn to sound continuously until the horn overheats and become inoperative.
Rotate the steering wheel while pressing the horn pad to identify intermittent and poor connections within the steering column.
If diagnosing a Horn- Poor Tone condition, inspect the following:
• | Debris or water in the horn assembly. |
• | Proper horn mounting hardware torque. Refer to Fastener Tightening Specifications. |
• | Debris in the joint where the horns attach to the vehicle. |
• | Debris in direct contact with the horn |
• | Vehicle components vibrating while the horn is sounding |
Horns System Description and Operation
Control Module References for scan tool information.
⇒ | If the test lamp is always ON or always OFF, refer to Horn Switch Circuit Test. |
⇒ | If the test lamp does not illuminate, test the control circuit terminal 18 at the BCM harness connector X5 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. |
⇒ | If the horns do not sound, refer to Right Horn Circuit Test. |
⇒ | If the sound emitted is not clear and even, refer to Right Horn - Poor Tone. |
⇒ | If the left horn does not sound, refer to Left Horn Circuit Test. |
⇒ | If the sound emitted is not clear and even, refer to Left Horn - Poor Tone. |
⇒ | If greater than the specified range, test the ground circuit for and open/high resistance. |
⇒ | If the test lamp is always ON, test the control circuit for a short to ground or a sticking horn switch. If the circuit tests normal, replace the BCM. |
⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage, an open high resistance, or a horn switch which is not closing. |
⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the underhood fuse block. |
⇒ | If greater than the specified range, test the ground circuit for and open/high resistance. |
⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the underhood fuse block. |
⇒ | If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, replace the underhood fuse block. |
⇒ | If the test lamp is always OFF and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the right horns. |
⇒ | If greater than the specified range, test the ground circuit for high resistance. |
⇒ | If greater than the specified range, test the control circuit for a high resistance. |
⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the HORN relay. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. |
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
⇒ | If the left horn does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the left horn. |
⇒ | If the test lamp is always ON, test the control circuit for a short to ground. |
⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. |
⇒ | If greater than the specified range, test the ground circuit for high resistance. |
⇒ | If greater than the specified range, test the control circuit for a high resistance. |
⇒ | If the sound emitted is not clear and even, test or replace the horn. |
⇒ | If not within the specified range, replace the relay. |
• | 30 and 86 |
• | 30 and 87 |
• | 30 and 85 |
• | 85 and 87 |
⇒ | If not the specified value, replace the relay. |
⇒ | If greater than the specified range, replace the relay. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for BCM replacement, setup and programming |
• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Horn Relay Control | 1 | 2 | B2750 00 | -- |
Horn Control | 2 | 2 | 1 | -- |
Horn Switch Ground | -- | 2 | 2 | -- |
Horn Ground | -- | 2 | 2 | -- |
1. Horn Always On 2. Horn Inoperative |
Battery positive voltage is applied at all times to the horn relay coil and horn relay switch. Pressing the horn switch applies ground to the horn relay control circuit. The body control module (BCM) also may apply ground to the horn relay control circuit. When the horn relay control circuit is grounded, the horn relay is energized and battery positive voltage is applied to the horn via the horn control circuit. The horn will sound as long as ground is applied to the horn relay control circuit.
A short to ground in the horn relay control circuit or a short to voltage in the horn control circuit will cause the horn to sound continuously until the horn overheats and become inoperative.
Rotate the steering wheel while pressing the horn pad to identify intermittent and poor connections within the steering column.
If diagnosing a Horn- Poor Tone condition, inspect the following:
• | Debris or water in the horn assembly. |
• | Proper horn mounting hardware torque. Refer to Fastener Tightening Specifications. |
• | Debris in the joint where the horns attach to the vehicle. |
• | Debris in direct contact with the horn |
• | Vehicle components vibrating while the horn is sounding |
Horns System Description and Operation
Control Module References for scan tool information
⇒ | If the test lamp does not illuminate or remains illuminated at all times, refer to Horn Switch Circuit Test. |
⇒ | If the test lamp does not illuminate, test the control circuit terminal 18 at the BCM for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. |
⇒ | If the horn does not sound, refer to Horn Circuit Test. |
⇒ | If the sound emitted is not clear and even, refer to Horn - Poor Tone. |
⇒ | If greater than the specified range, test the ground circuit for and open/high resistance. |
⇒ | If the test lamp is always ON, test the control circuit for a short to ground or a sticking horn switch. If the circuit tests normal, replace the BCM. |
⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage, an open high resistance, or a horn switch which is not closing. |
⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the underhood fuse block. |
⇒ | If greater than the specified range, test the ground circuit for and open/high resistance. |
⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the underhood fuse block. |
⇒ | If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, replace the underhood fuse block. |
⇒ | If the test lamp is always OFF and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the horn. |
⇒ | If greater than the specified range, test the ground circuit for a high resistance. |
⇒ | If greater than the specified range, test the control circuit for a high resistance. |
⇒ | If the sound emitted is not clear and even, replace the horn. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for BCM replacement, setup, and programming |