Powertrain, generic (extended)

P203F Reductant Level Too Low

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P203F is not a sensor fault but the result of the level monitor: the DEF tank holds too little fluid to keep the SCR system working. CARB requires light and medium duty diesels to flag an empty reductant supply (13 CCR 1968.2 (f)(2.2.3)(B)); a maker can be exempted if a driver inducement prevents running without DEF and every input to it, such as the level sensor, is monitored. Deutz stores P203F-00 as DEF tank level low on the EMR L1 main ECU, and FCA lists it among the codes that trigger the Service DEF – See Dealer message and later the limits. FCA bulletin 18-034-21 shows a trap on 2019–2021 Ram HD: ice covering the ultrasonic sensor can set P203F although the tank is full enough. Refill first; if the code returns, check P203A to P203E.

Likely causes

DEF tank actually low or empty
Frozen fluid or ice covering the level sensor
Leak at tank, lines or pump unit
Level sensor reading too low

Symptoms

  • Low DEF warnings and range countdown
  • Speed limit or no restart once the countdown ends
  • MIL on some vehicles

Repair estimate

DifficultyEasyDIY possible
Parts and labour€10–300
Time0.1–1 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reductant tankreductant level sensor

Related codes

P203AP203BP203EP2BAE

References: law.cornell.edu, serdia.deutz.com, static.nhtsa.gov, static.nhtsa.gov.