NOx Sensor 2 Voltage Low
Low voltage detected from the second NOx sensor.
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 second nitrogen oxide (NOx) sensor is sending a voltage signal below the expected range, indicating it might not be working right or there's a wiring issue.
What the computer is actually seeing
The NOx sensor should output a voltage between 0.1V to 4.8V based on NOx levels in the exhaust. If the voltage drops consistently below 0.1V, the ECM records this as SPN 4576.
What a healthy reading looks like
Normal operation should see voltages between 0.2V and 4.0V depending on NOx concentration.
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 connector for the NOx sensor for damage or corrosion. Repair if needed.
- 22. Measure the voltage at the sensor connector with the engine running. Are you getting a voltage between 0.2V and 4.0V? (Yes - go to step 4; No - go to step 3)
- 33. If voltage is low, replace the NOx sensor and recheck
- 44. Check for exhaust leaks around the sensor. Is there any? (Yes - repair the leak; No - go to step 5)
- 55. Clear the code, then take the vehicle for a test drive to see if the code reappears. Did it return? (Yes - replace the ECM; No - the issue is resolved.)
Common causes
- Faulty NOx sensor
- Wiring or connector issues
- Exhaust leaks
- ECM programming error
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's moderate severity; you can drive it, but fix it soon to prevent emissions issues.
Will this code come back after clearing?
It can if the underlying issue isn't fixed. Monitor the vehicle after repairs.
Why does it pair with other NOx codes?
These codes often indicate issues with the NOx sensor system, which can affect readings and trigger multiple codes.
Working a real vehicle right now?
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