Powertrain, generic (extended)

P203D Reductant Level Sensor A Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P203D is the high-side fault of level sensor A. On the LML Duramax and the 2014 Cruze 2.0D, GM samples level contact 1 1.5 ms after a test pulse: 3.56 to 4.74 V means an open load, above 4.74 V a short to battery, either one for more than 3 s with Type A. GM's 2017 diesel table uses a raw value above 95 (Type B), while the 2025 DEF controller sets P203D when the ultrasonic sensor reports a level beyond its 400 mm measuring range for 6 s. Preliminary bulletin PIP4887B for 2010–2011 Duramax trucks names P203D with P21AB and P21B0 and asks for wiring and terminal checks even on history codes before a new DEF tank. FCA (Ram 6.7L, 2014–2015) and Jaguar (2.0D, overfilled tank reading zero) list P203D as well. Low-side faults are P203C.

Likely causes

Open circuit, unplugged or loose tank connector
Signal wire shorted to supply or battery voltage
Overfilled tank on ultrasonic sensors
Failed level sensor or tank assembly

Symptoms

  • MIL with Service Exhaust Fluid System or similar message
  • DEF gauge missing or showing full permanently
  • Speed or restart limit if not repaired

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

P203AP203CP203BP21ABP21B0

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