C1266: ABS Valve Power Relay Circuit Failure

C1266 is a chassis code that sets when the ABS control module detects a fault in the power relay circuit that supplies the ABS hydraulic valve block. The valve power relay is responsible for energising the solenoid valves inside the ABS modulator during an ABS event, so if the relay circuit has failed, the module can't confirm the valves have proper power. The ABS warning light will typically illuminate and the anti-lock braking function will be disabled until the fault is resolved.

The most likely causes are a failed relay, a wiring fault in the relay control or supply circuit, or a corroded connector at the ABS module or relay. Check the ABS fuse and relay first as these are the quickest things to test and replace. If the relay and fuse are fine, the fault points to the wiring between the module and the relay, or in some cases a fault within the ABS module itself. A multimeter and wiring diagram for the relay circuit will let you verify supply and ground before replacing parts.

Severity is medium. The vehicle will still brake normally under most conditions, but you've lost the anti-lock protection that prevents wheel lock-up under heavy braking, which is particularly relevant on wet or loose surfaces. This is worth addressing promptly rather than leaving it open, and you should avoid situations requiring emergency braking until the ABS is back online and verified.