P20EE: 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 P20EE 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

12 complaints filed with NHTSA mention P20EE, 11 of them since 2015, across 8 different models. The component owners most often filed it under: engine.

Most-reported models

VehicleComplaintsModel years reported
RAM 150052014, 2015, 2016, 2017

Manufacturer service bulletins that name P20EE

296 technical service bulletins and manufacturer communications filed with NHTSA mention P20EE, from 12 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:

  • VOLVO VOLVO, bulletin 10179299: Diagnostic Trouble Code (DTC) P20EE - SCR NOx Catalyst Efficiency Below Threshold (Bank 1) - US17+OBD2019 And Newer Emissions
  • VOLVO VOLVO TRUCK, bulletin 10188149: Diagnostic Trouble Codes (DTC) P20EE And P103C, Diagnostic Procedure; - US17+OBD16 and US17+OBD2018 Emissions, Model Year 2018,2019
  • MACK MACK, bulletin 10188157: Diagnostic Trouble Codes (DTC) P20EE And P103C, Diagnostic Procedure; - US17+OBD16 and US17+OBD2018 Emissions, Model Year 2018,2019
  • HINO S-SERIES (2022, 2023, 2024), bulletin 10249762: Some customers may experience an illuminated Malfunction Indicator Light (MIL) with DTC P20EE Diesel Exhaust Fluid (DEF) System NOx Trap Low Efficiency set without an apparent cause. New calibrations for the DEF Control …
  • ISUZU N-SERIES (2022, 2023, 2024), bulletin 10249693: SERVICE BULLETIN: Some customers may experience an illuminated Malfunction Indicator Light (MIL) with DTC P20EE Diesel Exhaust Fluid (DEF) System NOx Trap Low Efficiency set without an apparent cause. New calibrations fo…
  • CHEVROLET SILVERADO 2500 (2024), bulletin 10254028: This service bulletin provides a service procedure to correct a customer concern of the Malfunction Indicator Lamp (MIL) Illuminated - DTC P062F, P040B, P041B, P0422, P060C, P062B, P1428, P142A, P20EE, P20FE, P22F9, P244…

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.