Powertrain, generic (extended)

P203C Reductant Level Sensor A Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P203C reports a level sensor A signal stuck at the bottom of its range. On GM's 6.6L LML and the 2014 Cruze diesel this is level contact 1: the tank electronics apply a test pulse, and a reading under 0.17 V for more than 3 s with over 8 V supply counts as a short to ground (LML Type A, Cruze Type B). GM's 2017/2018 diesel tables (1.6L Cruze, 2.8L Colorado) use a raw value below 2 in 40 of 50 samples, Type A, and the 2025 DEF controller sets the code on piezo excitation faults reported by the smart sensor. FCA lists P203C on 2014–2015 Ram 2500 to 5500 with the Cummins 6.7L and a radio frequency level sensor in the pump module; the fix was the pump/level module. GM's bulletin 12-06-04-002C ranks P203C among DEF codes that keep warnings active.

Likely causes

Signal wire shorted to ground or chafed at the tank
Level sensor or pump/level module internally faulty
DEF crept into the connector and bridges the terminals

Symptoms

  • MIL and DEF warning
  • DEF gauge reads empty or not at all
  • Speed or restart limit after a warning period

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–1,300
Time0.5–3 h

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

Parts involved

reductant level sensor

Related codes

P203AP203DP203BP21AAP21AF

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.