Powertrain, generic (extended)

P2AAF Diesel Fuel Presence Sensor Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2AAF reports the diesel presence sensor signal stuck above its upper limit. Common reasons are a signal wire touching a battery-fed line, an open ground or signal path that lets an internal pull-up drive the input high, or a sensor with a failed output stage. No manufacturer documents P2AAF publicly, and no public source states which signal level stands for diesel. The background is spelled out in Ford patent US10544031B2: diesel is heavier and oilier than gasoline, and once in a gasoline engine it can block injectors and burn uncontrolled, so the patent aims to stop the refill before the tank is full. With P2AAF set, such a warning can no longer be trusted. CARB demands range monitoring of such inputs; P2AAE is the low side, P2AAC the general circuit fault.

Likely causes

Signal wire shorted to a voltage source
Open sensor ground or signal wire
Sensor output stage failed

Symptoms

  • Check engine light on
  • Misfuelling warning unreliable

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€40–400
Time0.3–2 h

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

Parts involved

diesel fuel presence sensorwiring harnessecm

Related codes

P2AAEP2AACP2AAD

References: law.cornell.edu, patents.google.com.