P0638: owner reports and bulletins

Powertrain (generic, all makes). We haven't written the explanation for this code yet. Below is what owners and manufacturers have filed with NHTSA.

Got P0638 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

13 complaints filed with NHTSA mention P0638, 4 of them since 2015, across 8 different models. The component owners most often filed it under: engine.

Most-reported models

VehicleComplaintsModel years reported
KIA SORENTO32008, 2013

Manufacturer service bulletins that name P0638

5 technical service bulletins and manufacturer communications filed with NHTSA mention P0638, from 3 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:

  • MAZDA CX-9 (2016, 2017, 2018), bulletin 10170634: After parking the vehicle in temperatures below freezing, some customers may experience a lack of power with the check engine light on and DTCs P0638:00 and/or P2112:00 stored in memory. - P0638:00: Throttle valve actuat…
  • HYUNDAI SANTA FE, bulletin 10057210: HYUNDAI: SANTE FE 2010-2012; ECM SOFTWARE IS REQUIRED FOR 3.5L SANTE FE VEHICLES WITH MALFUNCTION CODES DTC P0638, DTC P2106, & P2110. *LJ
  • KIA SEDONA (2011, 2012, 2014, 2013), bulletin 10109712: TSB: SERVICE ACTION: ECM UPGRADE ? MIL ON WITH DTC P0638 AND ETC MOTOR CLEANING (SA153) - This bulletin provides information related to the ECM software upgrade for some 2011-2013MY Sorento 3.5L MPI vehicles, produced fr…

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.