C1203: ABS Outlet Valve Coil Rear Circuit Open

C1203 is a chassis code that indicates an open circuit in the coil that controls the rear ABS outlet valve. The outlet valve is part of the hydraulic control unit in your anti-lock braking system, and it manages brake fluid release during an ABS event. When the control module detects that the electrical circuit for this coil is broken, it logs C1203 and may disable ABS operation to prevent unpredictable braking behaviour.

An open circuit in this context usually points to a broken wire, a corroded connector, or a failed solenoid coil within the ABS hydraulic control unit. Start by inspecting the wiring and connectors running to the ABS modulator at the rear of the vehicle, looking for any visible damage, chafing, or moisture contamination. If the wiring checks out, the fault may lie in the hydraulic unit itself, which houses the solenoid coils and is not typically serviceable in isolation.

C1203 is rated medium severity. Your standard brakes will still function, but ABS may be partially or fully inactive, which reduces your stopping ability on slippery surfaces. This is worth booking in for diagnosis without delay, particularly if you drive in wet conditions. A qualified technician will need to confirm the circuit fault with a scan tool before replacing any components.