Circuit Description
The electronic brake control module (EBCM) receives a signal from the trailer ABS module over the ignition 1 voltage circuit. The EBCM applies ground to the trailer ABS indicator control circuit in order to turn ON the TRAILER ABS indicator.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step tests for an open in the trailer ABS indicator control circuit. If the fuse in the jumper wire opens while performing this test, the circuit is shorted to voltage.
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This step tests the circuit the trailer ABS module uses to send the frequency signal back to the EBCM.
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This step identifies devices that may cause interference with the frequency sent from the trailer ABS module.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Air Antilock Brake System Schematics | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
Does the TRAILER ABS indicator turn ON? | Go to Step 8 | Go to Step 3 | |
3 |
Does the test lamp illuminate? | Go to Step 5 | Go to Step 4 |
4 | Repair the open in the ignition 1 voltage circuit. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 13 | -- |
5 | Test the trailer ABS indicator control circuit for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 6 |
6 | Inspect the TRAILER ABS indicator bulb for an open or burned out filament. Did you find and correct the condition? | Go to Step 13
| Go to Step 7 |
7 | Replace the telltale circuit board. Refer to Telltale Circuit Board Replacement . Did you complete the replacement? | Go to Step 13 | -- |
Test the ignition 1 voltage circuit for an open between the EBCM and the trailer wiring harness connector. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 9 | |
9 | Verify that the trailer is equipped with ABS and is functioning properly. Does the trailer operate properly? | Go to Step 10 | Go to Step 12 |
Inspect for devices that may cause interference with the ABS signal from the trailer. Refer to Checking Aftermarket Accessories . Did you find and correct the condition? | Go to Step 13 | Go to Step 11 | |
11 | Replace the EBCM. Refer to Control Module References for replacement, setup, and programming Did you complete the replacement? | Go to Step 13 | -- |
12 | The problem is with the trailer. Refer to the trailer manufacturer. Did you complete the repair? | Go to Step 13 | -- |
13 | Verify the repair. Does the system operate normally? | System OK | Go to Step 2 |
