What it means
The reductant temperature is below the calibrated minimum. DEF/AdBlue may not flow correctly through the dosing system - heater fault or extreme cold weather.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
The diesel emissions system monitors reductant temperature so DEF/AdBlue can be delivered and dosed correctly. P2D45 sets when the measured temperature is below the system's calibrated minimum, which can happen in severe cold or when the reductant heater is not warming the fluid.
Common causes
Most likely first.
- Reductant heater failed
- Extreme ambient cold
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
- Record freeze-frame data and compare reductant temperature, ambient temperature, heater command, and warning or countdown status.
- Check whether the fault occurs only after a cold soak and whether the reductant temperature rises as the vehicle warms.
- Inspect accessible reductant heater wiring, connectors, and fluid lines for damage, leaks, or freezing.
- Use scan-tool data or supported active tests to check heater operation and temperature-sensor response.
- Test the heater circuit and sensor against the manufacturer's specification if the temperature remains low in conditions where warming should occur.
Common fixes
- Restore the vehicle to suitable operating conditions if the fault follows extreme cold and the heater is functioning.
- Repair damaged heater wiring or connectors.
- Replace a failed reductant heater.
- Repair a confirmed temperature-sensor or circuit fault.
Can I keep driving?
Address the warning promptly and follow any dashboard countdown; ignoring it can lead to reduced performance or a restart restriction, depending on the vehicle. Avoid assuming the DEF system is dosing correctly, since continued driving with this fault can increase NOx emissions and cause an inspection failure.
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.