Parts
$0-600+
U0121 — Lost Communication With ABS Control Module
CAUTIONIs it safe to drive? The ABS module isn't responding on the network. ABS, traction control, and stability control are likely off — normal brakes work, but ABS and stability assistance won't activate in a skid.
What U0121 means
Like U0101, this is a network fault, not necessarily a dead ABS module. The ABS module's fuse, power, ground, or its CAN connection is usually the culprit. ABS-dependent systems (traction, ESC) go offline with it.
Most likely causes (in order)
- Blown ABS module fuse or lost power/ground
- CAN bus wiring fault to the ABS module
- Corroded ABS module connector
- Failed ABS module
Symptoms you might notice
- ABS light on
- Traction and stability control off
- No ABS module communication on scan tool
What to check first
Check the ABS module fuses first. Verify power and ground at the module connector. If good, check CAN continuity between the ABS module and the gateway before replacing the module.
Repair cost & difficulty
Labor
0.5-5 hr
Difficulty
DIY-friendly