Reductant Quality Sensor, Fault
The system has detected a fault in the reductant quality sensor.
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 sensor checks if the diesel exhaust fluid (DEF) is good quality. If it's not, your engine management system raises this code to protect the emissions system.
What the computer is actually seeing
The reductant quality sensor sends a signal to the engine control module (ECM) based on the fluid quality. This signal should output a range between 0.5 to 2.5 volts; any voltage outside this range indicates a fault.
What a healthy reading looks like
Sensor output should be between 0.5V (good quality) and 2.5V (poor quality).
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. Ensure it’s at least 1/4 full. If it’s low, refill and clear the code.
- 22. Inspect the wiring harness and connector at the reductant quality sensor for damage or corrosion. Repair as needed.
- 33. Measure the voltage output of the reductant quality sensor using a multimeter. Check if it falls within the expected range (0.5V - 2.5V). If outside, replace the sensor.
- 44. If the sensor output is normal, perform a visual inspection of the DEF for contamination or quality issues. Replace if necessary.
- 55. Clear the code, and perform a test drive to see if the code returns.
Common causes
- Faulty reductant quality sensor
- Contaminated diesel exhaust fluid (DEF)
- Wiring issues or poor connections
- Faulty ECM
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, but driving long-term without addressing it may lead to further emissions system issues.
Will this code come back after clearing?
It can return if the underlying issue is not fixed, such as a faulty sensor or bad DEF.
Why does this code appear with other emissions codes?
Damage or faults in one part of the emissions system can impact others, so they often trigger simultaneously.
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