Powertrain, generic (extended)

P205B Reductant Tank Temperature Sensor A Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P205B is the rationality check of the DEF tank temperature: after a long cold soak every sensor should read about the same, so a tank value far off the rest is flagged. GM's 6.6L LML compares it with fuel temperature after 28,800 s engine off (beyond +35/−35 °C, Type B); GM's 2018 diesel table uses the exhaust gas temperature average (>35 °C, Type A), and the 2025 DEF controller needs at least four reference sensors and over 8 h off (>30 °C, Type A). Ford's 2023 diesels compare it with the quality sensor at start (>40 °C), VW's Touareg with outside air. Volvo/Mack (KC-2107) have it re-run before replacing the level sensor, and Ford (2019 6.7L), Land Rover (2016 TDV6) and GM (2021–22 3.0L) cured cases by software. Circuit faults are P205C/P205D.

Likely causes

Calibration error, fixed by reprogramming
Tank temperature sensor reading off (offset or gain)
Frozen tank or low fill level distorting the reading
Faulty reference sensor (fuel, exhaust or quality sensor)

Symptoms

  • MIL, sometimes with an emissions service message
  • Usually no change in driving

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–1,200
Time0.4–3 h

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

Parts involved

reductant tank temperature sensor

Related codes

P205AP205CP205DP205EP2043P2ADA

References: gsi.ext.gm.com, fordservicecontent.com, static.nhtsa.gov, static.nhtsa.gov.