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Home >> Alfa Romeo >> 2017 >> 4C Base >> Repair and Diagnosis (Single Page) >> Transmission >> Automatic Trans >> (C633/C635 DDCT Transmission - Electrical Diagnostics) >> DTC Troubleshooting >> U0121-00-Lost Communication With Antilock Brake System (Abs) Control Module >> Notes
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U0121-00-Lost Communication With Antilock Brake System (Abs) Control Module: Notes

For a complete wiring diagram, refer to appropriate SYSTEM WIRING DIAGRAMS article  .

Possible Causes
OPEN CAN CIRCUIT BETWEEN THE TRANSMISSION CONTROL MODULE (TCM) AND THE ANTILOCK BRAKE SYSTEM (ABS) MODULE
SHORT TO GROUND ON THE CAN CIRCUITS BETWEEN THE TCM AND THE ABS
SHORT TO BATTERY ON THE CAN CIRCUITS BETWEEN THE TCM AND THE ABS
LOOSE CONNECTION AT BODY CONTROL MODULE (BCM)
LOOSE CONNECTION AT TCM
POWER OR GROUND CIRCUIT FAULTS FOR BCM
BCM
TCM