U0121Medium urgency

Lost Communication with ABS Control Module

Network · CAN Bus

⚠️ Fix soon — ABS, traction control, and stability control may be disabled.

What this means

The main control network has lost communication with the ABS/ESC module. This disables all wheel speed-dependent safety systems including ABS, traction control, and electronic stability control.

Likely causes

Failed ABS/ESC moduleMost common
CAN bus wiring faultCommon
Blown ABS module fuseCommon
Corroded ABS module connectorCommon

Estimated repair cost

ABS module replacement$300 – $900

Wiring/connector repair$100 – $400

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Frequently asked questions

What does U0121 mean?

The main control network has lost communication with the ABS/ESC module. This disables all wheel speed-dependent safety systems including ABS, traction control, and electronic stability control.

Is U0121 serious?

Fix soon — ABS, traction control, and stability control may be disabled.

How much does it cost to fix U0121?

Repair costs for U0121 range from $300 – $900 depending on the root cause and your vehicle.

Can I drive with U0121?

You can drive short distances but should have it repaired within 1-2 weeks to prevent further damage.