P202B Reductant Tank Heater Control Circuit Low

P202B belongs to the electric heater in the DEF tank and reports a low reading in its control circuit. Generically that means a signal sitting too low, for example a grounded wire or a drive output pulled down. Volkswagen gives a concrete test on the 2014 Touareg 3.0 TDI: right at the start of heating the element's conductance must reach a minimum, and a value under 0.30 S, i.e. more than about 3.3 Ω, sets P202B. The element still conducts, unlike the open-circuit case P202A, but draws too little current to thaw the tank in time. Corroded pins, a partly damaged element or a wire chafed against the body are typical. The heater is needed only in frost, so the code often surfaces in the first cold weeks; while temperatures are mild, DEF dosing usually continues.

Likely causes

Symptoms

• Malfunction indicator lamp on
• DEF stays frozen longer after cold starts

Repair estimate

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

Parts involved

Related codes

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