NOx Exceedence - Insufficient Reagent Quality

Check these first

• Diluted or low-concentration DEF in the tank
• Contaminated DEF with water, dirt or the wrong fluid
• A failing DEF quality sensor misreading concentration
• A DEF dosing system that is not injecting enough reagent
• A failing SCR catalyst that cannot reduce NOx despite good DEF

What to do next

1. Check the DEF level and top off the tank with fresh DEF
2. Test the DEF concentration with a refractometer
3. Read DEF quality sensor data with a scan tool
4. Inspect the DEF dosing system for blockages or leaks
5. Replace the DEF quality sensor if its reading does not match a test
6. Clear the code and retest

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