P203B OBD II Trouble Code Reductant Level Sensor Circuit Range/Performance

How to quickly diagnose, repair, and causes of a P203B diagnostic code which indicates an unexpected electrical value from the reductant level sensor circuit.

Symptoms of P203B OBD II Trouble Code

  • Incorrect DEF (Diesel exhaust fluid) level reading
  • Exhaust emissions outside of specifications
  • CEL (Check engine light) on
  • Excessive smoke
  • "Low" or other DEF warning on instrument cluster

Common Causes of P203B OBD II Trouble Code

  • Reductant level sensor defective
  • Sensor's level arm obstructed mechanically inside storage tank
  • Wrong fluid in DEF storage tank
  • Electrical short

Severity of P203B OBD II Trouble Code

I would say this is a fairly minor code considering the possibilities. Essentially we are talking about a fault in a system that monitors what happens after it is already burnt and used. That said, most state/countries' emissions standards are fairly strict so it's a good idea to address this before it does more harm to your vehicle, not to mention the atmosphere!