P203CReductant Level Sensor A Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- MIL and DEF warning
- DEF gauge reads empty or not at all
- Speed or restart limit after a warning period
- Likely causes
- LikelySignal wire shorted to ground or chafed at the tank
- PossibleLevel sensor or pump/level module internally faulty
- PossibleDEF crept into the connector and bridges the terminals
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €1,300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.