C1234: 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 C1234 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

8 complaints filed with NHTSA mention C1234, 4 of them since 2015, across 4 different models. The component owners most often filed it under: service brakes.

Most-reported models

VehicleComplaintsModel years reported
TOYOTA SEQUOIA42001, 2002

Manufacturer service bulletins that name C1234

2 technical service bulletins and manufacturer communications filed with NHTSA mention C1234, from 1 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:

  • TOYOTA SEQUOIA (2001, 2002), bulletin 10129971: TSB: Some 2001 ? 2002 model year Sequoia vehicles may exhibit intermittent VSC activation. After the activation, Diagnostic Trouble Code (DTC) C1234 is stored in the skid control Electronic Control Unit (ECU) memory. Fol…

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.