For 1990-2009 cars only
Diagnostic Instructions
| • | 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. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Trailer ABS Indicator Control | -- | 1 | 1 | -- |
Driver Information Center (DIC) Ignition 3 Voltage | -- | 1 | -- | -- |
Trailer ABS indicator bulb | -- | 1 | -- | -- |
1. Circuit Inoperative | ||||
Circuit/System Description
The electronic brake control module (EBCM) receives a signal from the trailer Antilock Brake System (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.
Diagnostic Aids
| • | Disconnecting the trailer from the tractor checks if that was the cause of the Trailer ABS indicator illuminating. If upon disconnecting the trailer the Trailer ABS indicator stops illuminating check the trailer manufacturer. If no trailer was hooked to the tractor please proceed to Circuit/System Testing. |
| • | Inspect the Driver information Center (DIC) Trailer ABS Indicator Bulb for a open or burned out filament. |
| • | Inspect that the trailer is equipped with ABS and is operating properly. |
Reference Information
Schematic Reference
Air Antilock Brake System Schematics
Connector End View Reference
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for EBCM
Circuit/System Verification
- Ignition OFF for 5 seconds.
- Ignition ON, observe the Driver Information Center (DIC) Trailer ABS Indicator. The Indicator should illuminate then turn OFF.
Circuit/System Testing
- Ignition OFF, disconnect the electronic brake control module (EBCM) harness containing the trailer ABS indicator control circuit at the EBCM.
- Ignition ON, verify that a test lamp illuminates between the driver information center (DIC) ignition 1 circuit terminal 1 and ground.
- Verify the scan tool instrument cluster special function display test trailer ABS Lamps.
- Ignition OFF, disconnect the telltale circuit board circuit connector containing the trailer ABS indicator control circuit within the driver information center (DIC).
- Install a 3 A fused jumper wire between the EBCM control circuit terminal 11 and the DIC Ignition 1 voltage.
- Ignition OFF, Install a test lamp between the EBCM trailer ABS Indicator Control terminal 11 and ground.
- Ignition ON, verify that a test lamp does illuminate between the EBCM trailer ABS Indicator Control terminal 11 and ground.
- If all circuits test normal, replace the tell tale circuit board.
| ⇒ | If the test lamp does not illuminate, test the ignition 1 circuit for a short to ground or an open/high resistance. If the circuit tests normal, and the ignition 1 voltage circuit breaker is open, test the EBCM trailer ABS indicator control circuit terminal 11 for a short to ground. |
| ⇒ | If the test lamp illuminates, test the Ignition 1 voltage circuit for a open between the EBCM and the trailer wiring harness connector. If the circuit through the trailer tests normal, inspect for devices that may interfere with the ABS signal refer to Checking Aftermarket Accessories. |
| ⇒ | If the trailer ABS lamp does not illuminate, test the EBCM control circuit terminal 11 for a short to voltage. |
| ⇒ | If the circuit tests normal, replace the EBCM. |
| ⇒ | If the trailer ABS indicator does not turn OFF, test the ABS indicator control circuit for a short to ground and open/high resistance. If the circuit tests normal, replace the telltale circuit board. |
| ⇒ | If not the specified value, test the signal circuit, for an open/high resistance. If the circuit tests normal, replace the EBCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for EBCM replacement, setup, and programming |
