Reductant A Quality Problem
The system has detected a problem with the quality of the urea solution in the DEF system.
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)
Your vehicle's computer thinks there's something wrong with the diesel exhaust fluid (DEF) quality, which could mean it's too diluted, contaminated, or not meeting the specification.
What the computer is actually seeing
The engine control module (ECM) monitors the DEF quality via sensors. It's looking for a specific conductivity level that indicates the concentration of urea. If the conductivity falls outside a predetermined range, it'll trigger this code.
What a healthy reading looks like
DEF should have a urea concentration of about 32.5% in a solution. Conductivity readings should match manufacturer specs, typically around 1000-1500 µS/cm.
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 the DEF level in the tank. Make sure it's full and not diluted with water or other fluids. Decision: If DEF is low or contaminated, refill or replace the DEF.
- 22. Inspect the DEF quality sensor and wiring for damage or loose connections. Decision: Repair or replace wiring/connectors if needed.
- 33. Measure the DEF quality with a conductivity meter if available. Check against expected values (1000-1500 µS/cm). Decision: Replace DEF if readings are out of spec.
- 44. If all checks are good and code persists, replace the DEF quality sensor. Decision: Clear the code and drive vehicle to see if it returns.
Common causes
- Diluted or contaminated DEF
- Faulty DEF quality sensor
- Issues with the DEF injector or lines
- Air trapped in the DEF system
Typical repair cost
$$-$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, but drivability may be affected as the system will limit power if the DEF quality is not corrected.
Will this code come back after clearing it?
If the underlying issue isn't resolved, yes, it will return.
Why does this code pair with other codes?
It's common as multiple issues can occur in the DEF system affecting performance.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
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