C0278 ABS Solenoid Relay Circuit Malfunction

Category: Chassis
Severity: Check Engine Light
Applies to: Tacoma, Tundra, 4Runner with ABS

What does C0278 mean on a Toyota?

C0278 — ABS Solenoid Relay Circuit Malfunction. This Toyota-enhanced code applies to Tacoma, Tundra, 4Runner with ABS.

Common causes of C0278

Failed ABS solenoid relay
Open relay control circuit
Blown ABS solenoid fuse
Corroded relay socket
Skid control ECU driver fault

How to fix C0278

Check ABS fuses
Swap the solenoid relay with a known-good unit
Test relay control voltage
Inspect the socket
Verify ABS function returns after repair