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U0121

Lost Communication with ABS Module

Medium — fix within daysDrive with caution

Severity: Fix within days. Drive with caution and watch for new symptoms.

What U0121 means

Another module cannot talk to the ABS module over the data network, so anti-lock braking and traction control may be off.

Common causes

How to fix it

Check fuses and wiring first, then have a shop trace the network fault.

Can I drive with U0121?

The regular brakes still work, but ABS and traction control are off. Drive carefully.

Related codes

Questions, answered

Is it safe to drive with code U0121?

You can drive short distances carefully; watch for worsening symptoms. The regular brakes still work, but ABS and traction control are off. Drive carefully.

What causes code U0121?

The most common causes are: Damaged data wiring; Blown fuse; Failing ABS module; Corroded connector. A scan tool and a visual check of the parts above is where a technician starts.

How do I fix code U0121?

Check fuses and wiring first, then have a shop trace the network fault.

Not repair advice. This page gives general information about code U0121 only. Cars differ by make, model and year — confirm the fault with a scan tool and have the repair done by a qualified technician.

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