C0121ABS

ABS Valve Relay Circuit

C0121 indicates a fault in the ABS valve relay circuit. This relay powers the ABS solenoid valves, and when it fails the module cannot operate the valves and disables ABS.

🚗 Yes, but ABS and stability control are disabled, so fix it promptly.

HIGH

severity

🎯 Top Causes, Ranked by Likelihood

#1Failed valve relay$20-$200

35%

The relay (often internal to the ABS module) has failed.

#2ABS module (EBCM) failure$400-$1200

30%

Internal relay or driver in the module has failed.

#3Wiring or connector fault$50-$300

20%

Damaged power or control wiring to the relay.

#4Low system voltage$100-$300

15%

Weak battery or charging system trips the relay fault.

🩺 Common Symptoms

ABS warning light on
Traction and stability control lights on
ABS self-test does not complete
Brake pedal may feel firm

💰 Repair Cost: DIY vs Shop

DIY Cost

$20-$300

Shop Cost

$150-$1200

📋 Free OBD2 Code Cheat Sheet

The 50 most common codes with likely cause and DIY fix cost. Sent once, no spam.

🔧 How to Diagnose C0121

1Scan and record all ABS codes

2Check battery and charging system voltage

3Inspect ABS module power, ground, and connectors

4Test relay operation with a scan tool if the relay is serviceable

❓ Frequently Asked Questions

Can I drive with C0121?

Yes, normal braking works, but ABS and stability control are disabled. Drive carefully and fix it soon.

How much to fix C0121?

If it is a serviceable relay it can be cheap, but an internal module fault can run $400-$1200.

What causes C0121 most often?

A failed valve relay, an internal ABS module fault, or low system voltage.

🔗 Related Codes

C0110C0161C0800C0265