Powertrain, generic (extended)

P2D86 Fuel Temperature Sensor A/B Correlation

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P2D86 checks two fuel temperature sensors against each other. Where both ought to show nearly the same value, because they measure the same fuel or after a long engine-off soak, a gap larger than a calibrated margin makes the pair implausible, without telling which sensor lies. No manufacturer documents P2D86 publicly. GM runs exactly this test on direct-injection gasoline engines under its own number P111F: two SENT temperature sensors on the high-pressure rail may differ by no more than 10 °C, and 100 bad readings out of 125, one every 100 ms, set a Type B fault after two trips. Ford's 2023 diesels instead compare sensor A with the charge air cooler outlet after six hours off (P0181, 20 °C). Circuit faults of the single sensors are P0182/P0183 and P0187/P0188.

Likely causes

One of the two fuel temperature sensors has drifted and reads too warm or too cold

Corroded or loose connector adding resistance to one sensor signal

Replacement sensor of the wrong type or fitted in the wrong position

Engine control software with too tight a comparison limit

Symptoms

Malfunction indicator lamp, usually after two drives
Often no noticeable change in how the engine runs
Occasionally rougher hot restarts if fuel quantity correction is off

Repair estimate

DifficultyMediumDIY possible

Parts and labour€60–400

Time0.5–2 h

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

Parts involved

fuel temperature sensor afuel temperature sensor becm

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