Powertrain, generic (extended)

P205A Reductant Tank Temperature Sensor A Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P205A is the general circuit code for the temperature sensor inside the DEF tank, usually built into the level or heater unit; the separate sensor in the supply path uses P2042 ff. Deutz assigns the tank temperature (J1939 SPN 3031) to P205A: failure type 13 for an open circuit, 21 and 22 for values under or over the valid range, while the SCR-side DEF sensor (SPN 4337) stays with P2042. VW's 2014 Touareg (CNRB) stores P205A when the signal exceeds 4.70 V, i.e. the high side that an open NTC circuit produces, and keeps the low side (below 0.30 V) for P205C. Other makers split these faults into P205C and P205D. The tank temperature decides when the tank heater runs, so a fault can mean frozen DEF and an SCR warning in winter.

Likely causes

Open circuit or loose tank connector
Tank temperature sensor in the sender unit defective
Corroded terminals from DEF exposure

Symptoms

  • MIL and DEF warning
  • Tank heating not working in frost
  • Speed or restart limit on some models

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–1,200
Time0.5–3 h

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

Parts involved

reductant tank temperature sensorreductant tank

Related codes

P205BP205CP205DP205EP2042P2ADE

References: serdia.deutz.com, serdia.deutz.com, static.nhtsa.gov.