Reductant Quality Issue
The engine control module has detected a problem with the quality of the diesel exhaust fluid (DEF).
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 computer thinks the urea solution (DEF) isn't right, which can make your emissions system not work properly.
What the computer is actually seeing
The engine control module (ECM) monitors the concentration and quality of the diesel exhaust fluid (DEF) via the DEF quality sensor. It expects a specific urea concentration (around 32.5%) and will throw this code if the reading is outside acceptable limits.
What a healthy reading looks like
DEF must have a urea concentration of 32.5%. If the vehicle has a DEF quality sensor, it should read between 10-30% conductivity for good quality DEF.
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. Check DEF level in the tank. Is it low? If yes, top off with the correct DEF (32.5% urea).
- 22. Inspect the DEF tank for contamination or leaks. Any signs of contamination? If yes, clean or replace as necessary.
- 33. Check the wiring and connectors for the DEF quality sensor. Any breaks or corrosion? If yes, repair the wiring/connectors.
- 44. Test the DEF quality sensor with a scan tool. Is it providing a reading within acceptable range? If no, replace the sensor.
- 55. If all above checks are good but the code persists, test DEF fluid quality with a conductivity meter. Is it between 10-30%? If no, drain and refill with proper DEF.
Common causes
- Dirty or contaminated DEF in the tank
- Faulty DEF quality sensor
- Wiring or connector issue in the DEF system
- Incorrect DEF concentration (e.g. mixing with water)
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
No, it's not safe to drive as it can affect emissions and lead to further damage to the SCR system.
Will this code come back after clearing it?
If the underlying issue isn't fixed, yes, it will likely return.
Why does this issue often come with other codes?
Problems with DEF quality typically affect the entire emissions system, triggering related fault codes.
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