Zoeken
U0121
Systeem
Network (CAN Bus)
Scanner vereist
Full-system scanner (engine, ABS, SRS, transmission, service resets)

Lost Communication with ABS Control Module

Understand U0121, common causes, and the right TOPDON scanner to diagnose it.

ABS module not communicating — ABS, stability control, and sometimes cruise may be disabled.

Veelvoorkomende symptomen

  • ABS light on
  • Traction control off
  • C-codes may accompany

Typische oorzaken

  • ABS module failure
  • Wheel speed sensor wiring damaging comm
  • Low voltage
  • Blown ABS fuse

Welke scanner heb je nodig?

Full-system scanner (engine, ABS, SRS, transmission, service resets)

Gebruik live data en freeze frame voordat je onderdelen vervangt. ABS-, SRS- en U-codes vereisen meestal een full-system scanner.

Diagnosetips

  • Leg freeze frame vast wanneer de code voor het eerst verschijnt
  • Wis de code pas na het oplossen van de oorzaak
  • Controleer op gerelateerde pending codes
  • Controleer of accuspanning boven 12,4 V is voordat je sensoren suspecteert

Aanbevolen TOPDON scanners

Veelgestelde vragen

What does U0121 mean?
U0121 indicates lost communication with abs control module. ABS module not communicating — ABS, stability control, and sometimes cruise may be disabled.
Can I diagnose U0121 with a basic code reader?
U0121 may set in the engine module, but related diagnostics often benefit from an enhanced or full-system scanner with live data and freeze frame.
Which TOPDON scanner do I need for U0121?
Full-system scanner (engine, ABS, SRS, transmission, service resets) See recommended tools on this page.
Is it safe to drive with U0121?
It depends on the code and symptoms. Flashing check engine lights and misfire codes should be addressed immediately. Consult a professional if unsure.