C0277 critical

ABS Valve Relay Circuit Open

The C0277 code means the vehicle's onboard diagnostic system has detected: ABS Valve Relay Circuit Open. This is a critical severity code.

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Keep driving?: Short distances only
DIY difficulty: hard
Estimated cost: $50 - $500 (parts and labor)

Read ABS Codes

BlueDriver Bluetooth Pro Scanner

Basic scanners cannot read ABS codes. BlueDriver reads all systems including ABS, SRS, and transmission through your phone.

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Read ABS Codes

LAUNCH CRP123X (Reads ABS + Chassis)

Basic scanners cannot read ABS codes. This one reads all four systems so you know exactly which sensor failed.

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Common Symptoms

ABS completely disabled
ABS and TC warning lights both on
ABS does not activate during hard braking
No ABS pump motor sound during braking
Stability control inoperative

Probable Causes (Ranked by Likelihood)

Failed ABS valve relay Very High
Open circuit in relay wiring High
Corroded ABS relay connector Moderate
ABS module relay driver failure Low

Step-by-Step Diagnostic Procedure

Locate and test ABS valve relay
Check relay connector for corrosion
Test relay coil and contacts with multimeter
Swap relay with identical known good relay
Check wiring from ABS module to relay

Frequently Asked Questions

Is the ABS valve relay the same as the ABS motor relay?

No. The valve relay controls power to the solenoid valves inside the ABS module, while the motor relay controls the hydraulic pump motor. Both must function for the ABS system to work.

Can I swap the relay to test it?

Many vehicles use the same relay part number for multiple functions. You can temporarily swap the ABS relay with another identical relay in the fuse box to test if the relay is the problem.

Where is the ABS valve relay?

It is typically located in the under-hood fuse and relay box, though some vehicles integrate it into the ABS module itself. Check your owner's manual or fuse box cover for the relay location.