P203C code meaning
Reductant Level Sensor A Circuit Low
Powertrain system Generic code P20xx codes Check engine light
What P203C means
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.
P203C at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P203C
- MIL and DEF warning
- DEF gauge reads empty or not at all
- Speed or restart limit after a warning period
Common causes of P203C
- Most 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
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant level sensor
What each part of P203C means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 0 | Area: fuel and air metering and auxiliary emission controls. |
| 3C | The exact fault in that area. |
What to do next
- Note P203C and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P203C
What does P203C mean?
P203C means "Reductant Level Sensor A Circuit Low". P203C reports a level sensor A signal stuck at the bottom of its range. It is a generic code, so it means the same on every make.
Is it safe to drive with P203C?
Drive gently and only to a workshop. With P203C the car can go into limp mode (reduced power) to protect itself.
Will P203C fail an emissions test?
Yes, it can. P203C is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P203C to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P203C clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.