OBD II Fault Code

  • OBD II P203F

OBD-II Code Engine may not start is defined as a Reductant Level Too Low

Diesel Exhaust Fluid (DEF) is used to assist in converting leftover exhaust particles to harmless gases. In order to burn off those particles, the temperature of the exhaust system needs to increase. the injection of DEF Fluid into the exhaust stream brings Diesel Particulate Filter (DPF) up to temperature. The system is then able to convert harmful NOx to Nitrogen, Carbon Dioxide, and water. The Reductant Catalyst (SRC) was added to further reduce any NOx was still in the exhaust stream. The Reductant Level Sensor tells the engine computer (PCM) how much DEF is left in the tank. If the PCM sees that the DEF level is too low, code P203F is set. Additional warnings may be present on the instrument cluster. Failure to add DEF fluid may result in the engine not restarting until more DEF fluid is added.

Engine may not start Symptoms

  • DEF low fluid warning on instrument cluster
  • Engine may not start

Common Problems That Trigger the P203F Code

  • DEF is too low
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