Reductant Quality Issue
This code indicates that the diesel exhaust fluid (DEF) is of poor quality or contaminated.
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 engine's computer checks the quality of the diesel exhaust fluid. If the fluid has too much urea, too many contaminants, or has frozen, it won't work properly.
What the computer is actually seeing
The engine control module (ECM) monitors the reductant quality using a sensor. If the readings are outside the expected range for DEF quality, it triggers this code.
What a healthy reading looks like
The DEF should contain 32.5% urea and 67.5% deionized water. If the urea concentration is too low or too high, or if the fluid is contaminated, the quality is unacceptable.
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. Inspect the DEF level and quality. Ensure it is clean and not contaminated. Decision: If contaminated, replace DEF. If okay, proceed to step 2.
- 22. Check the ambient temperature. If below 12°F (-11°C), ensure the DEF is thawed. Decision: If frozen, allow to thaw. If not, proceed to step 3.
- 33. Test the wiring and connectors for the DEF quality sensor. Look for loose connections or signs of damage. Decision: Repair any issues found. If intact, proceed to step 4.
- 44. Use a scan tool to monitor DEF quality readings. Compare values to expected values for DEF. Decision: If readings are out of range, replace the DEF quality sensor. If within range, consult further diagnostics.
Common causes
- Contaminated DEF (water, dirt, or improper additives)
- Frozen DEF due to low ambient temperatures
- Faulty DEF quality sensor
- Faulty wiring or connector to the DEF quality sensor
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's generally not safe to drive long distances as it can lead to reduced emissions performance and potential engine derate.
Will the code come back after clearing?
If the underlying issue isn't resolved, the code will likely return.
Why does this pair with other codes?
It often pairs with issues related to DEF quality and SCR system failures, which are interconnected for emissions control.
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