Diagnostic Instructions
Circuit/System Description
The electronic brake control module (EBCM) activates the traction control (TC) modulator valve by supplying 12 volts to the TC modulator valve high reference circuit and supplying ground to the TC modulator valve low reference circuit. When the TC modulator
valve energized an internal valve opens and air pressure is applied to the drive axle brake pressure modulator valve (BPMV).
Conditions for Running the Diagnostic Fault
| • | The EBCM is calibrated for traction control. |
Conditions for Setting the Diagnostic Fault
The EBCM detects an open or shorted TC modulator or circuitry.
Action Taken When the Diagnostic Fault Sets
| • | The TC system is disabled. |
| • | The Traction OFF indicator on turns ON. |
| • | Driver is unable to re-enable the TC system. |
| • | The Bendix Remote Diagnostic Unit (RDU), illuminates the TRC and MOD LEDs. |
Conditions for Clearing the Diagnostic Fault
| • | Repair the condition responsible for illuminating the status lamps. |
Diagnostic Aids
Important: Upon any electronic brake control module (EBCM), or TC modulator valve replacement perform the Bendix RDU magnet reset procedure. Refer to
Status Lamp Resetting.
Reference Information
Schematic Reference
Air Antilock Brake System Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Air ABS Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References
Circuit/System Verification
Ignition ON, observe the Bendix Remote Diagnostic Unit (RDU). The LEDs on the RDU should indicate a current traction control modulator fault.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the (TC) traction control valve.
- Ignition OFF, test for value range within 0.5-12 ohm between the traction control (TC) modulator high circuit terminal A and low circuit terminal B.
| ⇒ | If not within the specified range, test the signal circuits for an open/high resistance, short to ground, short to voltage, or shorted together. If the circuits test normal, replace the traction control (TC) control valve. |
| ⇒ | If within the specified range, test or replace the electronic brake control module (EBCM). |
- If all circuits test normal, test or replace the (TC) control valve..
Component Testing
- Ignition OFF, disconnect the harness connector at the (TC) traction control valve.
- Ignition OFF, test for value range within 0.5-12 ohm between the traction control (TC) modulator high circuit terminal A and low circuit terminal B.
| ⇒ | If within the specified range, test or replace the electronic brake control module (EBCM). |
- Test for infinite resistance between each terminal and the sensor housing/case.
| ⇒ | If less than the specified value, replace the (TC) traction control valve. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
