P202BReductant Tank Heater Control Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- Malfunction indicator lamp on
- DEF stays frozen longer after cold starts
- Likely causes
- LikelyCorroded heater connector pins adding resistance
- PossibleHeater element partly damaged, resistance too high
- RareControl wire chafed through to ground
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.