Powertrain, generic (extended)

P203E Reductant Level Sensor A Circuit Intermittent/Erratic

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P203E stands for a level sensor A signal that keeps dropping out or jumping. FCA explains it best: Ram HD trucks with the 6.7L Cummins (2019–2021) carry an ultrasonic level sensor that needs an air gap above the fluid. Bulletin 18-034-21 and STAR case S2025000001 name an overfilled tank as the main trigger, because the echo no longer returns; residual ice or urea crystals in the focus tube after hard frost do the same. Returned parts were mostly found free of faults. The test only runs with ambient and tank above about 4 °C, so the fix is draining 2 to 3 gallons or thawing the tank, then about 15 min of steady highway driving. Jeep and Ram 3.0L EcoDiesel software updates (18-018-14, 18-018-15) also cover P203E. Steady circuit faults belong to P203C/P203D.

Likely causes

DEF tank overfilled, no air space for the ultrasonic echo
Residual ice or urea crystals covering the sensor
Intermittent contact at the tank connector
Control unit software needing an update

Symptoms

  • MIL and Service DEF message
  • DEF gauge jumps or reads 0 % with fluid in the tank
  • Warning returns after filling or after a cold night

Repair estimate

DifficultyEasyDIY possible
Parts and labour€0–900
Time0.3–2 h

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

Parts involved

reductant level sensor

Related codes

P203AP203BP203FP21ACP21B1

References: static.nhtsa.gov, static.nhtsa.gov, law.cornell.edu.