ABS Valve Relay Circuit Open
What does C0277 mean?
The C0277 code means the vehicle's onboard diagnostic system has detected: ABS Valve Relay Circuit Open. This is a critical severity code.
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
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Locate and test ABS valve relay
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Check relay connector for corrosion
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Test relay coil and contacts with multimeter
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Swap relay with identical known good relay
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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.