Is it safe to drive with a U0121 code?

Severity is medium. Address U0121 sooner rather than later — driving with an active check engine light can worsen the problem or void emissions warranties.

How much does it cost to fix U0121?

Repair costs for U0121 typically range from $80 to $1500 in the US, depending on the underlying cause. The most common fix is: Failed ABS module.

What are the symptoms of U0121?

ABS light on. Traction control disabled. Speedometer issues (newer cars).

Check Engine Code

U0121

Lost Communication With Anti-Lock Brake System (ABS) Module

Severity: medium DIY difficulty: 3/5 Typical cost: $80–$1500

What U0121 means

ABS module has dropped off the bus. Triggers ABS warning light and disables stability control.

Symptoms

ABS light on
Traction control disabled
Speedometer issues (newer cars)

Likely causes (most common first)

Failed ABS module
Damaged wiring
Power/ground issue at ABS module
CAN bus fault

Can I keep driving?

Medium — drivable but fix soon

Typical repair cost

DIY fixes can start near $80 (parts only). Shop repairs for U0121 typically run up to $1500 depending on the underlying cause and vehicle. Start with the most common cause — Failed ABS module — before throwing parts at it.

Related codes

U0100 U0101U0140C0561

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