P20FE: Reductant Metering Unit 1 Performance

What does P20FE mean?

P20FE judges whether the first reductant metering unit actually delivers the quantity the SCR control asks for. GM's 2025 Duramax tables average a delivery compensation factor and set the code, Type A after one trip, once that factor passes 1.44, meaning the expected pressure drop no longer proves correct dosing. VW Group uses it on 3.0 TDI models: Porsche reflashed 2015–2016 Cayenne Diesel because the check was too sensitive in the cold; Audi tied it on 2012–2015 Q7 to a loose filter housing letting unfiltered AdBlue damage the pressure sensor and pump; VW's 2015 Touareg tip first checks the injector part number, then runs the metering quantity test. GM also updated software for it (23-NA-193, 24-NA-058). Unit 2 is P2EAD.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Malfunction indicator lamp on
• AdBlue/DEF system warning in the cluster
• Higher NOx, possible SCR efficiency codes (P20EE)

Common causes

• High Partly blocked or crystallised dosing injector
• Medium Loose or damaged tank filter letting debris reach pump and sensor
• Medium Over-sensitive diagnostic calibration (software update available)
• Low Air in the dosing lines after service or low fluid level

Likelihood is a general estimate across vehicles; your make and model may differ.