P20F3
SCR NOx Pre-Catalyst Efficiency Below Threshold
This code indicates scr nox pre-catalyst efficiency below threshold (bank 2). It relates to the emissions: nox, particulate, dpf, scr and may affect performance, emissions, or drivability depending on the exact failure.
SCR NOx Pre-Catalyst Efficiency Below Threshold (Bank 2)
Common causes
- medium
Sensor failure
O2, NOx, pressure, or temperature sensors can drift or fail.
Typical part cost: $100-400
- medium
Exhaust leak or restriction
Leaks before sensors or a restricted exhaust can set emissions codes.
Typical part cost: $100-400
See all causes + fix costs
Create a free Wrenchify account to unlock the rest for P20F3.
Unlock causesFree forever · No credit card
First things to check
- 1Confirm the code with a scan tool and check for additional related codes.
- 2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.
Get the full step-by-step diagnosis
Create a free Wrenchify account to unlock the rest for P20F3.
Unlock diagnosisFree forever · No credit card
Related codes
See related trouble codes
Create a free Wrenchify account to unlock the rest for P20F3.
Unlock related codesFree forever · No credit card
Frequently asked questions
What does P20F3 mean?
P20F3 means "SCR NOx Pre-Catalyst Efficiency Below Threshold (Bank 2)". It is a generic OBD-II code that points to a fault in the emissions: nox, particulate, dpf, scr.
Can I keep driving with this code?
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical. Use the Wrenchify app for a full diagnosis specific to your vehicle.
Get the full P20F3 diagnosis for your vehicle
Year, make, model + step-by-step repair help — free plan included.