P1870: 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 P1870 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

23 complaints filed with NHTSA mention P1870, 1 of them since 2015, across 13 different models. The component owners most often filed it under: power train:automatic transmission.

Most-reported models

VehicleComplaintsModel years reported
CHEVROLET S1051997, 1998, 1999, 2000
CHEVROLET BLAZER41996, 1998, 1999, 2002

Manufacturer service bulletins that name P1870

4 technical service bulletins and manufacturer communications filed with NHTSA mention P1870, from 2 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:

  • CHEVROLET BLAZER (1998, 1999, 2000, 2001), bulletin 10096073: THIS PRELIMINARY INFORMATION COMMUNICATION PROVIDES INFORMATION TO THE TECHNICIAN ABOUT VEHICLE THAT AFTER A TRANSMISSION OR TORQUE CONVERTER REPLACEMENT THE VEHICLE MAY HAVE A HARSH 1-2 UPSHIFT AND THE CHECK ENGINE LIGH…
  • GMC JIMMY (1998, 1999, 2000, 2001), bulletin 10096073: THIS PRELIMINARY INFORMATION COMMUNICATION PROVIDES INFORMATION TO THE TECHNICIAN ABOUT VEHICLE THAT AFTER A TRANSMISSION OR TORQUE CONVERTER REPLACEMENT THE VEHICLE MAY HAVE A HARSH 1-2 UPSHIFT AND THE CHECK ENGINE LIGH…
  • CHEVROLET ASTRO (1998, 1999, 2000, 2001), bulletin 10114916: This Preliminary Information communication provides information to the technician about vehicle that after a transmission or torque converter replacement the vehicle may have a harsh 1-2 upshift and the Check Engine Ligh…
  • GMC G SERIES (1999, 2000, 1998, 2001), bulletin 10114916: This Preliminary Information communication provides information to the technician about vehicle that after a transmission or torque converter replacement the vehicle may have a harsh 1-2 upshift and the Check Engine Ligh…

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.