Test C: The Anti-Lock Brake System (ABS) Module Does Not Respond To The Scan Tool

PINPOINT TEST C: THE ANTI-LOCK BRAKE SYSTEM (ABS) MODULE DOES NOT RESPOND TO THE SCAN TOOL

C1-C2:

C3-C4:

Normal Operation
The ABS module communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits VDB04 (WH/BU) (HS-CAN +) and VDB05 (WH) (HS-CAN -) provide the network connection to the ABS module. The ABS module shares the HS-CAN network with the powertrain control module (PCM), the transmission control module (TCM), the restraints control module (RCM), the four wheel drive (4WD) control module (if equipped), the air suspension module (if equipped) and the instrument cluster. Voltage for the ABS module is provided by circuit CBB77 (WH), and ground is provided by circuit GD120 (BK/GN).

DTC U0121 - sets in a module which had attempted to communicate with the ABS control module and failed.

Possible Causes
- Fuse
- Circuit CBB77 (WH) open
- Circuit GD120 (BK/GN) open
- Circuit VDB04 (WH/BU) open (HS-CAN +)
- Circuit VDB05 (WH) open (HS-CAN -)
- ABS module