C1203: owner reports and bulletins

Chassis. We haven't written the explanation for this code yet. Below is what owners and manufacturers have filed with NHTSA.

Got C1203 on your scanner? Tell the mechanic your year, make, model and any symptoms and you'll get the likely cause and what to check first. Ask about this code.

What owners report to NHTSA

18 complaints filed with NHTSA mention C1203, 8 of them since 2015, across 5 different models. The component owners most often filed it under: service brakes.

Most-reported models

VehicleComplaintsModel years reported
TOYOTA SEQUOIA122002, 2003, 2004
TOYOTA SEQUOIA SR532003

Manufacturer service bulletins that name C1203

1 technical service bulletins and manufacturer communications filed with NHTSA mention C1203, from 1 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:

  • KIA OPTIMA HYBRID (2015), bulletin 10089848: "TECH TIP: DTC C1203 OR C1212 - SPEED SENSOR FAILURE SYMPTOM: C1203 RH FRONT WHEEL SPEED SENSOR OPEN/SHORT AND/OR C1212 VEHICLE SPEED SENSOR FAILURE. REPAIR: CHECK FOR A SHORT IN THE MAIN ESC HARNESS NEAR THE RADIATOR BR…

Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.