U0121
Lost Communication with ABS Control Module
System: Network
Severity: medium
What does U0121 mean?
The DTC U0121 (Lost Communication with ABS Control Module) is a fault code stored by the ECU when it detects a lost comm ABS condition in the network subsystem. It is commonly seen on European and Asian vehicles using Bosch, Continental, Siemens or Denso ECUs.
Common causes of U0121
- Failed ABS module
- CAN wiring fault
- ABS power supply
- Wheel speed sensor connector backfeed
How to fix U0121
Check ABS power + fuses. Common on older VAG when SAI bridge fails.
Tuning approach with DaVinci Deluxe
For U0121, DaVinci Deluxe offers the following ECU map adjustments and software solutions:
- (ABS module repair required)
Need to fix U0121 on your ECU?
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