Powertrain, generic (extended)

P20E6 Reductant Injection Air Pressure Too Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

This code belongs to air-assisted DEF dosing, where compressed air carries the fluid to the nozzle and breaks it into fine droplets; airless pump systems in cars and most current pickups do not use it. P20E6 means the air pressure in the dosing branch stays below the minimum the control unit needs while dosing is requested. A Cummins patent for such a system gives an example limit: if the combined air and DEF pressure remains under about 300 kPa for 10 s, a low-pressure fault is stored, pointing to a weak air supply or compressor, a shut-off valve that does not open, blocked or leaking lines, or crystallised DEF blocking the air path. Cummins bulletin TSB200096 describes crystal build-up on the air side of such dosing units that cuts air flow. No maker documents P20E6 itself publicly. Leakage is P20CA, excess pressure P20E7.

Likely causes

Insufficient air tank pressure from a leak or weak compressor
Air shut-off or pressure control valve not opening
DEF crystals restricting the air side of the dosing unit
Leaking, kinked or blocked air line to the doser

Symptoms

  • Check engine light and SCR warning
  • DEF dosing reduced or stopped, rising NOx emissions
  • Engine derate after the inducement period

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–900
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reductant air pumpreductant air pressure control valvereductant air line

Related codes

P20E7P20CAP20ABP2038P2059

References: patents.google.com, static.nhtsa.gov, law.cornell.edu.