U0121: Lost Communication with ABS Module
4 vehicles · 4 makes · $80-$3,200 repair
U0121 is an OBD-II diagnostic trouble code meaning “Lost Communication with ABS Module.” Communication lost with the ABS control module. ABS, traction, and stability control are disabled. This code appears across 4 vehicle models from 4 manufacturers, with repair costs ranging from $80 to $3,200.
Common Causes
Typical Repair Cost
Based on 5 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose U0121, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
Vehicles Affected (4)
FAQ
What does U0121 mean?
U0121 stands for "Lost Communication with ABS Module." Communication lost with the ABS control module. ABS, traction, and stability control are disabled.
What are the most common causes of U0121?
The most common causes of U0121 are: ABS module failure, CAN bus wiring fault, Module power loss, Corroded CAN connector, Fuse blown. The specific cause varies by vehicle.
How much does it cost to fix U0121?
Repair costs for U0121 range from $80 to $3,200, depending on the vehicle and root cause.
Which vehicles are affected by U0121?
Au7o has documented U0121 across 4 vehicle models from 4 manufacturers: Dodge, Ford, GMC, Mercedes-Benz.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.