P203B Reductant (AdBlue) level sensor A circuit range/performance
What P203B means
The AdBlue tank has a level sensor, usually built into the pump and heater assembly. P203B means its reading does not make sense, for example it does not change as AdBlue is used or jumps around. The car may show wrong AdBlue range warnings and can start a start-restriction countdown.
P203B is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- Medium
- Typical repair cost
- 120–800 €
- Workshop time
- 1–4 h
- Repair difficulty
- Hard
- DIY possible
- No
- Check engine light
- Yes
- Affects emissions test
- Yes
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- AdBlue level warning despite a full tank
- AdBlue range display wrong or jumping
- Check engine light on
- Possible start-restriction countdown
Common causes
- Faulty level sensor in the AdBlue tank module
- Crystallised or contaminated AdBlue around the sensor
- Frozen AdBlue in cold weather
- Damaged wiring or corroded connector at the tank
- Wrong fluid added to the AdBlue tank
Can I keep driving with P203B?
You can drive, but have it checked within one or two weeks. Keep the tank topped up and watch for a countdown warning.
What to check first
- Check the AdBlue level and make sure the correct fluid is in the tank
- Inspect the tank module connector and wiring for corrosion
- Compare the level reading in live data with the actual level after topping up
- Replace the level sensor or tank module if the reading stays wrong (often supplied as one assembly)
Related codes
- P2017 Intake manifold runner position sensor/switch circuit high (bank 1)
- P2015 Intake manifold runner position sensor/switch circuit range/performance (bank 1)
- P2014 Intake manifold runner position sensor/switch circuit (bank 1)
- P2008 Intake manifold runner control circuit/open (bank 1)
- P2006 Intake manifold runner control stuck closed (bank 1)
- P2004 Intake manifold runner control stuck open (bank 1)
- P2003 Diesel particulate filter efficiency below threshold (bank 2)
- P2002 Diesel particulate filter efficiency below threshold (bank 1)
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
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