Powertrain, generic (extended)

P2D91 Engine Oil Pressure Sensor/Switch C Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P2D91 says sensor C is electrically in range, but its reading does not fit the engine's state: pressure while the engine stands still, too little at speed, or a value that stays frozen while conditions change. Ford's 2024 summary handles sensor A this way under P0521, catching a signal stuck high, low or mid-range and readings that depart from a modelled pressure in either direction for 5 to 10 s. A GM 2024 engine table sets P0521 after 3 s, two-trip, when relative pressure exceeds 500 kPa under defined conditions or stays below 50 kPa above 1520 rpm. No manufacturer documents P2D91 publicly. A tired sensor, sludge in its bore, wrong oil grade, a worn pump or a sticking pressure control valve can be behind it; confirm real pressure with a mechanical gauge. Electrical faults are P2D8F/P2D90.

Likely causes

Sensor C drifted or stuck at one value
Real oil pressure deviation from worn pump, wrong oil or low oil level
Sticking oil pressure control valve of a variable pump
Sludge or debris in the sensor bore

Symptoms

  • Malfunction indicator lamp after two drives on some makes
  • Oil pressure warning flickers or appears without reason
  • Possible engine noise if pressure is really low

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–1,500
Time0.5–4 h

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

Parts involved

engine oil pressure sensor cwiring harnessecm

Related codes

P2D8EP2D8FP2D90P0521P055BP0524

References: fordservicecontent.com, gsi.ext.gm.com, law.cornell.edu.