Circuit Description
The vehicle horns are activated whenever ground is applied to the horn relay coil through the horn relay control circuit. Ground may be applied by either of the following:
| • | Body control module (BCM) |
| • | Horn switch |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2753 Horn Relay Coil Circuit High
Conditions for Running the DTC
| • | The Body Control System voltage must be between 9.0-16.0 volts. |
| • | The BCM is commanding the horn relay to energize or the horn switch is pressed. |
Conditions for Setting the DTC
The BCM detects a short to voltage in the horn relay control circuit for approximately 500 milliseconds.
Action Taken When the DTC Sets
| • | The horns are inoperative from the BCM and the horn switch. |
| • | The BCM stores DTC B2753 in memory. |
Conditions for Clearing the DTC
| • | A current DTC will clear when the fault is no longer present and the ignition switch is cycled. |
| • | A history DTC will clear after 100 consecutive ignition cycles without a fault present. |
| • | A scan tool may be used to clear history and current DTCs. |
Diagnostic Aids
| • | Always begin diagnosis with the first DTC listed on the scan tool. |
| • | The scan tool must display DTC B2753 as a current code before performing these diagnostics. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Listen for an audible click when the horn relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
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Tests for voltage at the coil side of the horn relay. The HORN fuse supplies power to the coil side of the horn relay.
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Verifies that the BCM is providing ground to the horn relay.
-
Tests if ground is constantly being applied to the horn relay.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Horn Schematics | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Does the horn relay turn ON and OFF with each command? | Go to Diagnostic Aids | Go to Step 3 | |
Does the test lamp illuminate? | Go to Step 4 | Go to Step 10 | |
Does the test lamp turn ON and OFF with each command? | Go to Step 8 | Go to Step 5 | |
Does the test lamp remain illuminated with each command? | Go to Step 7 | Go to Step 6 | |
6 | Test the horn relay control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
7 | Test the horn relay control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
8 | Inspect for poor connections at the horn relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 11 |
9 | Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 12 |
10 | Repair the battery positive voltage circuit of the horn relay coil. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 13 | -- |
11 | Replace the horn relay. Did you complete the replacement? | Go to Step 13 | -- |
12 | Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 13 | -- |
13 |
Does the DTC reset? | Go to Step 2 | System OK |
