What it means
The control module detects an SCR NOx catalyst inlet temperature below its calibrated threshold. This can delay or limit SCR NOx reduction.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The SCR catalyst inlet temperature sensor or related temperature input tells the emissions control module how hot the exhaust is before it enters the SCR catalyst. The module sets this code when the reported inlet temperature is below its calibrated threshold during monitored conditions. A faulty sensor or circuit can report a false low temperature, while genuinely cool exhaust can also delay effective NOx reduction.
Common causes
Most likely first.
- SCR inlet temperature sensor or circuit fault
- Exhaust temperature genuinely too low under monitored conditions
Symptoms
- Check engine light
How to diagnose it
- Capture freeze-frame data and compare the reported SCR inlet temperature with engine load, warm-up state, and other exhaust temperature readings.
- Inspect the SCR inlet temperature sensor connector and wiring for corrosion, loose connections, or heat damage.
- Check for exhaust leaks or operating conditions that could keep the catalyst inlet genuinely cool during the monitored drive.
- Test the temperature sensor circuit and compare its reading with the manufacturer's diagnostic specification.
- If the sensor and circuit pass, investigate engine or exhaust conditions that may prevent the SCR inlet from reaching operating temperature.
Common fixes
- Repair a loose or corroded temperature-sensor connection.
- Repair damaged sensor wiring.
- Replace the SCR inlet temperature sensor if it fails the specified test.
- Repair an exhaust leak or underlying engine condition causing genuinely low exhaust temperature.
Can I keep driving?
The code usually does not make the vehicle immediately unsafe to drive, but SCR emissions control may be reduced and the vehicle may fail an emissions inspection. Avoid ignoring related emissions warnings, especially if an AdBlue/DEF countdown appears.
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.