What it means
The reductant level sensor circuit signal is intermittent or erratic. The code does not identify a particular cause.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The DEF level sensor A reports tank level to the control module. P203E sets when its signal changes intermittently or erratically, rather than staying consistently too low or too high, so the reported level may jump or drop out.
Common causes
Most likely first.
- Corroded sender contact
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
How to diagnose it
- Save freeze-frame data and graph sensor A level to see whether the fault coincides with movement, vibration, or a particular tank level.
- Inspect the sender connector for corrosion or loose pin fit and the harness for rubbing against a vibrating or moving component.
- With the scan tool displaying live level, gently move the accessible harness and connector to check for signal dropouts.
- Check circuit continuity and the supply, ground, and signal for interruptions, comparing results with the manufacturer's specification.
- If the wiring remains stable but the reading still jumps, inspect the sender contact or float mechanism and replace the faulty sensor assembly.
Common fixes
- Clean and secure corroded or loose sender contacts.
- Reroute and secure a harness that rubs or vibrates, then repair damaged insulation.
- Replace a sender with an intermittent contact or faulty level mechanism.
Can I keep driving?
If the vehicle runs normally, cautious driving is usually possible, but verify the DEF level and repair the fault soon because the reading may change unexpectedly. The warning can progress to a start countdown, and the emissions system may not operate as intended.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.