P2044
Reductant Temperature Sensor A Circuit Low
Emissions (SCR / DEF after-treatment)
Generic OBD-II
Medium
What it means
P2044 means the reductant (diesel-exhaust-fluid) temperature sensor A is reporting an abnormally low circuit voltage, so the SCR system can't accurately gauge DEF temperature. The engine starts and runs normally, but NOx dosing may be affected and many diesels start a derate countdown if it isn't fixed. The usual cause is a shorted sensor, wiring, or connector.
Medium
Can I keep driving? The engine runs and starts normally, but the SCR system may not dose correctly and some diesels count down to a speed limit — don't leave it unfixed.
Common symptoms
What you'll notice
- Check-engine light on
- SCR / diesel-exhaust-fluid (DEF) warning message
- Higher NOx emissions; may fail an emissions test
- Speed / power derate if the fault persists (varies by vehicle)
Common causes
Most likely first
- Reductant (DEF) temperature sensor A shorted or reading lowLikely
- Sensor circuit wiring shorted to groundCommon
- Corroded or loose connector at the DEF tank / sensorCommon
- Failed reductant temperature sensorLess often
- PCM / dosing control module fault (least likely)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and check for companion reductant codes (P2042, P2043).
- Inspect the DEF temperature sensor connector and wiring for a short to ground or corrosion.
- Compare the sensor's reported temperature to ambient/other sensors with a scan tool.
- Replace the reductant temperature sensor if out of spec, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P2044?+
Mechanically yes — the engine runs fine. But the SCR system may not work correctly, and many diesels begin a derate countdown, so address it before that limits the vehicle.
Can I just clear P2044?+
It returns until the sensor or wiring is repaired, and clearing won't stop an emissions derate from recurring.
Related codes
Often seen with P2044
Read & clear P2044 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX