SCR NOx Sensor Circuit Range/Performance Problem
The SCR NOx sensor is not reading within expected parameters.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The sensor that measures nitrogen oxides (NOx) in the exhaust system is either not sending the right signals or has a problem causing it to give false readings.
What the computer is actually seeing
The Engine Control Module (ECM) detects that the voltage signals from the NOx sensor are outside of normal limits, which ideally should be between 0.5-4.5 volts during operation.
What a healthy reading looks like
Normal operating voltage from the NOx sensor should range from 0.5V to 4.5V, reflecting changes in NOx levels during engine operation.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect the wiring and connectors for any damage, corrosion, or loose connections related to the NOx sensor.
- 22. Check for exhaust leaks that might affect the NOx sensor's readings.
- 33. Use a multimeter to measure the voltage at the NOx sensor connector. Expect a voltage between 0.5V and 4.5V. If outside this range, replace the sensor.
- 44. Clear the fault codes and take the vehicle for a test drive to see if the SPN 4366 code returns.
Common causes
- Faulty NOx sensor
- Wiring issues or connector problems
- Exhaust system leaks
- SCR system malfunction
Typical repair cost
$$ (200-600)
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's best to fix this soon as it affects emissions and can lead to issues with the SCR system.
Will this code return after clearing it?
Yes, if the underlying issue isn't resolved, the code will likely reappear after a short period of driving.
Why does this code often pair with other SPN codes?
These codes can be related to the same NOx sensor system or other components in the SCR system that are interconnected.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →