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OBD-II · Engine and powertrain (P)

P20BA

AdBlue heater A control circuit performance

What it means

AdBlue heater A (usually in the tank) is not heating as expected, judged from its current or from temperature change. The exact heater depends on the car.

Symptoms

  • AdBlue/emissions warning, possibly with a no-start countdown
  • AdBlue problems in cold weather

Likely causes, most likely first

Likely causes, most likely first
No.Cause
01failing heater element in the tank module
02high resistance in the connector or wiring
03AdBlue temperature sensor fault
04low supply voltage

What to check, step by step

  1. 01Check battery and charging voltage.
  2. 02Inspect connector and wiring at the tank.
  3. 03Measure heater resistance and current with a diagnostic tool test.
  4. 04Replace the tank module/heater if out of specification.