Reductant Temperature Sensor A Circuit High
What it means
P2045 means the signal from the reductant (diesel exhaust fluid / DEF) temperature sensor A is too high — usually an open or a short to voltage in the circuit, or a failed sensor. The SCR system uses this reading to dose DEF correctly and reduce NOx, so a fault can disable emissions control and, on many diesels, trigger a power-derate countdown.
Can I keep driving? Drivable in the short term, but many diesels start an emissions derate countdown that progressively limits power until the SCR fault is fixed.
Real-world scan data
Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.
Common symptoms
What you'll notice
- Check-engine light on
- SCR / DEF or emissions-system warning message
- Possible reduced power or an emissions derate countdown
Common causes
Most likely first
- Faulty reductant (DEF) temperature sensorLikely
- Open or short-to-voltage in the sensor wiringCommon
- Corroded or loose connector at the sensorCommon
- Failed PCM / reductant control module (rare)Less often
How to diagnose & fix
Work through it in order
- Scan freeze-frame and note any companion SCR/DEF codes.
- Inspect the sensor's connector and wiring for opens or shorts to voltage.
- Measure the sensor's resistance/signal against spec.
- Replace the reductant temperature sensor if it's out of range.
- Clear the code and complete a drive cycle to confirm the SCR monitor.
FAQ
Quick answers
Is it safe to drive with P2045?+
Can I just clear P2045?+
Related codes
Read & clear P2045 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.