P1238: owner reports and bulletins

Powertrain (manufacturer-specific). We haven't written the explanation for this code yet. Below is what owners and manufacturers have filed with NHTSA.

Got P1238 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

2 complaints filed with NHTSA mention P1238, 1 of them since 2015, across 2 different models. The component owners most often filed it under: fuel system, diesel.

Manufacturer service bulletins that name P1238

2 technical service bulletins and manufacturer communications filed with NHTSA mention P1238, from 2 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:

  • CHEVROLET F SERIES (2004, 2005), bulletin 10113006: This Preliminary Information communication provides information to the technician about vehicles that have Misfire, rough running, surge, chuggle, and possible Service Engine Soon Malfunction Indicator Lamp on. Technicia…
  • GMC G VAN BUS (2004, 2005), bulletin 10113006: This Preliminary Information communication provides information to the technician about vehicles that have Misfire, rough running, surge, chuggle, and possible Service Engine Soon Malfunction Indicator Lamp on. Technicia…

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.