Circuit Description
The horn circuit is part of a standard horn system except for the addition of a relay and the BCM providing a control circuit. The BCM can ground the horn relay control circuit in order to energize the relay and turn ON the horns, allowing the horns to be used for Universal Theft Deterrent (UTD) and Remote Function Actuation functions (RFA). The BCM monitors the voltage level on the horn control circuit. When the BCM commands the relay ON, the voltage level on the control circuit should be low. When the relay is OFF, the voltage level should be high. If the BCM detects a voltage level other than expected, a malfunction is present and a DTC will set.
Conditions for Setting the DTC
| • | The BCM detects a high voltage level (a short to voltage or BCM open internally) in the horn relay control circuit. |
| • | The BCM can only test for this condition with the horn relay energized. |
| • | All conditions must be present for 2 seconds. |
Action Taken When the DTC Sets
| • | Stores a DTC B2528 in the BCM memory. |
| • | No driver warning message will be displayed for this DTC. |
Conditions for Clearing the DTC
| • | This DTC requires an ignition cycle in order to change from current to history. |
| • | The BCM no longer detects a high voltage level in the horn relay control circuit only with the horn relay energized. |
| • | A history DTC will clear after 50 consecutive ignition cycles if the condition for the malfunction is no longer present. |
| • | Use the IPC clearing DTCs feature. |
| • | Use a scan tool. |
Diagnostic Aids
| • | The following conditions may cause an intermittent malfunction: |
| - | There is an intermittent open or short to voltage in the horn relay control circuit. |
| - | There is low resistance in the relay coil. |
| - | There are poor connections at the BCM, the underhood electrical center, or the horn relay terminals. |
| - | The horn relay is shorted to voltage internally. |
| • | If the BCM is open internally the BCM cannot provide horn control functions. If the horn relay control circuit is shorted to voltage, the horn will remain OFF at all times. |
| • | The horn relay may be installed in the I/P electrical center in two directions and still function properly. Refer to Electrical Center Identification in Wiring Systems for electrical center circuit identification. |
| • | If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while moving related wiring and connectors. This can often cause the malfunction to occur. Refer to Intermittents and Poor Connections . |
Test Description
The number(s) below refer to the step number(s) 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.
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Verifies that the BCM is providing ground to the Horn relay.
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Tests if ground is constantly being applied to the Horn relay.
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Tests for a short to voltage in the Horn control circuit.
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When the BCM is replaced, use a scan tool to perform the BCM RPO Reprogram procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration .
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the BCM Diagnostic System Check? | -- | Go to Step 2 | |
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 | |
Test the control circuit of the Horn relay 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 control circuit of the Horn relay 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 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 coil side feed circuit of the Horn relay. Refer to 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 | -- |
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Important: Perform the BCM RPO Reprogram procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration . Replace the BCM. Refer to Body Control Module Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | |
13 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
