OBD-II code · Powertrain (generic, extended)
P202B Reductant Tank Heater Control Circuit Low
The DEF tank heater control line reads below the expected voltage — short to ground or stuck-low driver.
Is it safe to drive with P202B?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyShort to ground
- Less likelyConnector pins corroded - high contact resistance
- Less likelyHarness chafing through insulation
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.7–2.5 h
- Emissions test
- Likely to fail
- Parts involved
- Reductant Tank Heater
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.