Powertrain, generic (extended)

P202A Reductant Tank Heater Control Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

DEF freezes at about −11 °C, so the tank carries an electric, often PTC-type heater that thaws enough fluid for dosing after a cold start. P202A covers the control circuit of that heater with the emphasis on an open circuit: when commanded on, practically no current flows. Volkswagen documents it on the 2014 Touareg 3.0 TDI (CNRB) and judges the element by its conductance: during heating a value of 0.10 S or less, roughly 10 Ω or more, sets the code. Typical are a broken element, a burnt or loose connector at the tank, a blown fuse or an interrupted wire. With the heater dead, frozen DEF cannot be dissolved, so in winter the system soon reports it cannot dose and may begin the inducement countdown. P202B and P202C separate a weak or excessive heater current from this complete interruption.

Likely causes

Tank heater element burnt through
Loose or burnt connector at the tank, or blown heater fuse
Interrupted wire between control unit and tank

Symptoms

  • Malfunction indicator lamp on
  • In frost, DEF system warning and inducement countdown

Repair estimate

DifficultyMediumWorkshop job
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

reductant tank heaterreductant tank harness

Related codes

P202BP202CP209FP205B

References: static.nhtsa.gov, law.cornell.edu, en.wikipedia.org.