Aftertreatment 1 Diesel Exhaust Fluid Quality Error
Indicates 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 is checking the DEF for proper quality. If the quality is off, it could mean the fluid is contaminated or diluted, affecting emissions control.
What the computer is actually seeing
The system monitors the conductivity and urea concentration of the DEF. If the readings fall outside acceptable parameters, it triggers this code.
What a healthy reading looks like
Conductivity should be between 1200-1600 uS/cm and urea concentration should be around 32.5% for proper 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 fluid level: Should be between min and max markers. If low, top off with correct DEF.
- 22. Inspect DEF fluid for contamination: Check for discoloration or particulates. If contaminated, replace the DEF.
- 33. Test the DEF quality sensor: Use a scan tool to read conductivity and urea concentration values. Compare with expected values.
- 44. Check wiring and connections to the DEF quality sensor for damage or corrosion.
- 55. If all looks good, consider replacing the DEF quality sensor if readings are still out of range.
Common causes
- Low DEF fluid level
- Contaminated DEF
- Using incorrect DEF type
- Faulty DEF quality sensor
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It’s not recommended to drive for long with this code, as it can affect emissions and might lead to further issues.
Will this code go away on its own?
The code will not clear if the underlying issue isn’t resolved. Fix the problem to clear the code.
Why does this code pair with other SPN codes?
Multiple SPNs can indicate related issues in the DEF system, showing that other components may also need attention.
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