P3056: 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 P3056 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

3 complaints filed with NHTSA mention P3056, 3 of them since 2015, across 2 different models. The component owners most often filed it under: electrical system.

Manufacturer service bulletins that name P3056

8 technical service bulletins and manufacturer communications filed with NHTSA mention P3056, from 3 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:

  • CHEVROLET SILVERADO 1500 (2019, 2020, 2021), bulletin 10190415: This Preliminary Information provides information to the technician about a additional diagnostic tip for a check engine lamp for DTC P3055 and P3056 and the start/Stop being inoperative.
  • GMC SIERRA 1500 (2019, 2020, 2021), bulletin 10190415: This Preliminary Information provides information to the technician about a additional diagnostic tip for a check engine lamp for DTC P3055 and P3056 and the start/Stop being inoperative.
  • CHEVROLET BLAZER (2020, 2021), bulletin 10195156: This engineering information (EI) is requesting information from technicians to perform the check list provided and contact the engineer listed in regards to the Malfunction Indicator Lamp illuminated on Driver Informati…
  • BUICK LACROSSE (2017, 2018), bulletin 10139238: This technical bulletin provides a procedure to clean out the HVAC drain hose if a vehicle has a condition of Front Carpet Wet and/or Musty Smell with Possible DTC P3055 or P3056 due to the water coming inside.
  • CHEVROLET MALIBU (2016), bulletin 10089338: 43890 - SERVICE UPDATE. CERTAIN VEHICLES, EQUIPPED WITH STOP/START ENGINE CONTROL OPTION, MAY ILLUMINATE THE MALFUNCTION INDICATOR LAMP (MIL) AND SET DIAGNOSTIC TROUBLE CODES (DTC) P3055 AND P3056. THIS CONDITION COULD R…

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.