Reductant Quality Issue
There’s 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 monitors the purity of the diesel exhaust fluid and if it senses that the fluid is contaminated or not meeting quality standards, it sets this code.
What the computer is actually seeing
The engine control module (ECM) checks the conductivity and/or the urea concentration in the DEF. If the readings deviate significantly from expected standards, it logs this issue.
What a healthy reading looks like
The DEF should have a urea concentration of about 32.5% with a specific conductivity of 5-10 mS/cm; contamination or incorrect mixture will trigger the code.
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 that the DEF tank is full and contains the correct type of fluid (32.5% urea). Decision: Is the DEF quality correct? Go to step 2 if yes; otherwise, replace DEF.
- 22. Inspect the DEF quality sensor wiring and connector for damage or corrosion. Decision: Is the wiring good? Proceed to step 3 if yes; otherwise, repair or replace wiring as necessary.
- 33. Test the DEF quality sensor using a multimeter to confirm it is functioning properly. Expected voltage should align with manufacturer specifications (typically around 0.5-4.5V depending on concentration). Decision: Is the sensor good? If yes, clear the code and retest; if no, replace the sensor.
Common causes
- Defective or contaminated diesel exhaust fluid (DEF)
- Faulty DEF quality sensor
- Wiring issues between DEF sensor and ECM
- Incorrectly filled DEF tank (e.g., water or other substances)
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
While you can technically drive, it may lead to reduced performance or prevent proper exhaust treatment, so fix it soon.
Will this issue return after clearing the code?
If the underlying problem isn't resolved, the code will likely come back after driving for a short time.
Why is this paired with other codes?
Codes involving DEF often trigger together due to shared systems and sensors, like fluid quality or injector issues.
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