U0121

A dead battery, A faulty ABS module, A problem with ABS module circuit, A problem with the CAN bus

OBD-II diagnostic trouble code U0121indicates a fault detected by the vehicle's onboard computer. This code applies to all OBD-II compliant vehicles and should be addressed promptly to avoid potential engine or emissions system damage.

Severity Level 4 — Serious

This code indicates a serious issue that can cause noticeable driveability problems and potential engine damage if not addressed. The vehicle should be taken to a mechanic as soon as possible. Extended driving is not recommended.

Common Symptoms

• Multiple warning lights
• Gauges may not work
• Vehicle may not start

Possible Causes

• A dead battery, A faulty ABS module, A problem with ABS module circuit, A problem with the CAN bus
• Fault in related component or circuit

Common Fixes

• Scan with OBD2 diagnostic tool
• Inspect related components and wiring

Estimated Repair Cost

These are estimated costs based on generic repair data. Actual costs may vary depending on your vehicle, location, and labor rates.

Explore Repair Costs

Related Discussions

See what other car owners are saying about this code and related repairs.