Normal Operation
The ABS module uses information received from several sensors (wheel speed sensors, steering wheel rotation sensor, stability/traction control system sensors, etc.) to determine if vehicle stability, traction or roll warrants ESC or RSC® interaction. If an event is going to occur, the ABS module adjusts the brake torque at specific wheels and the PCM reduces engine torque to make the vehicle more stable. Once the ABS module has determined that the stability event has been corrected, it returns the brake and engine torque to normal and continues to monitor the vehicle. DTCs set in the ignition cycle can only be cleared by cycling the ignition off and on once the fault has been corrected. The Restraints Control Module (RCM) measures the yaw rate and vehicle acceleration, then sends the signal through a secondary, dedicated Controller Area Network (CAN) to the ABS module. The ABS module uses this information for AdvanceTrac® and RSC® system operation. The ABS module also compares this information to information it receives from other sensors (brake pedal input, steering wheel) to determine how valid the information is and to determine if an instability event is about to occur.
The RCM and the ABS module communicate along circuits VCA23 (BU/WH) and VCA24 (GN/OG). An open circuit or a short to power or ground on any one of these circuits will cause the ABS module to set a DTC. Also, if the RCM is not mounted in the correct position, with the electrical connector facing the rear of the vehicle, the ABS module will also set DTCs.
| DTC Description | Fault Trigger Condition | ||
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If the ABS module receives a message from the RCM that is out of the normal operating range or one that does not agree with other sensor information, the appropriate signal fault DTC will be set. | ||
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If conditions or DTCs exist that prevent the AdvanceTrac® and RSC® systems from operating, DTCs C1963 and/or C1975 will be set. This DTC is usually set due to the steering wheel rotation sensor or the RCM being damaged or installed incorrectly. | ||
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The RCM uses a dedicated communication bus to send information to the ABS module. If, during normal operation, the ABS module does not receive any information from the RCM for more than 250 milliseconds, DTC U0151 or U0452 will be set. U0151 monitors both the HS-CAN and the dedicated CAN circuits. If the ABS module does not receive the RCM serial number, over the HS-CAN, DTC U0151 sets. It also sets if the sensor data is not received over the dedicated CAN from the RCM. | ||
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This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- RCM
- ABS module