Powertrain, generic (extended)

P20E7 Reductant Injection Air Pressure Too High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

On air-assisted DEF dosing the control unit regulates the compressed air fed into the mixing chamber so that the nozzle sprays a stable mist. P20E7 is set when the measured air pressure climbs above the permitted upper limit, for instance because the pressure control valve no longer throttles and passes full tank pressure, or because the path downstream of the sensor is narrowed so pressure builds up in front of it. Cummins bulletin TSB200096 shows how DEF crystals form in the air solenoid and the nozzle of air-assisted dosers, restricting flow and distorting the spray pattern. A skewed air pressure sensor gives the same reading. Airless systems in passenger cars do not have this circuit. No maker documents P20E7 publicly; CARB requires the air-assisted delivery to be monitored. Low pressure and leakage are P20E6 and P20CA.

Likely causes

Air pressure control valve no longer regulating and passing full supply pressure
DEF crystals or deposits restricting the nozzle or mixing path
Air pressure sensor reading too high

Symptoms

  • Check engine light and SCR warning
  • Irregular DEF spray, deposits in the exhaust and higher NOx
  • Engine derate if dosing is shut down

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–900
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 valve

Related codes

P20E6P20CAP20AAP20A7P2038

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