Powertrain, generic (extended)

P202C Reductant Tank Heater Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P202C is the high-side fault of the DEF tank heater circuit: the module sees a value above the allowed range, as when the wire touches battery positive or an element that conducts far too well. On the Touareg 3.0 TDI of model year 2014, Volkswagen flags it when the element's conductance at the start of heating exceeds 0.62 S, below roughly 1.6 Ω, which hints at an internal short. On 2025 Ram 2500 to 5500 with the 6.7 L Cummins, Chrysler's bulletin 08-076-26 lists P202C next to other DEF heater and pressure codes and cure them with new software for the DEF control unit; there the fault came from calibration, not from hardware. With a real short the fuse may blow or the driver protect itself, so the tank stays unheated. In winter the system may then warn and count down to a speed limit.

Likely causes

DEF control unit calibration (software update on some models)
Heater element with internal short, resistance too low
Heater control wire shorted to battery voltage

Symptoms

  • Malfunction indicator lamp on
  • Service DEF message, later speed limited
  • Heater fuse may blow

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–1,500
Time0.3–4 h

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

Parts involved

reductant tank heaterreductant control module

Related codes

P202AP202BP209FP20BC

References: static.nhtsa.gov, static.nhtsa.gov, en.wikipedia.org.