Reductant Quality Sensor Range/Performance Problem
The reductant quality sensor is reading outside expected range.
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What it means (plain English)
The sensor that checks if the diesel exhaust fluid (DEF) is good quality is sending a signal that something's off, either due to contamination or a faulty sensor.
What the computer is actually seeing
The engine control module (ECM) sees irregular readings from the reductant quality sensor, indicating the DEF might be bad or the sensor itself is malfunctioning.
What a healthy reading looks like
The voltage output from the reductant quality sensor should range between 0.5V to 4.5V depending on the fluid quality; anything outside this range triggers a fault 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. Inspect the wiring and connectors for the reductant quality sensor for damage or corrosion. Repair any found issues. Decision: If fixed, clear codes and retest. If still present, proceed to step 2.
- 22. Check the quality of the diesel exhaust fluid (DEF) in the tank. Use only OEM or certified fluid. Decision: If contaminated or expired, replace the DEF and retest. If quality is good, proceed to step 3.
- 33. Test the reductant quality sensor operation using a multimeter. Expected output voltage should range from 0.5V to 4.5V based on fluid quality. Decision: If out of range, replace the sensor. If within range, check ECM for faults.
Common causes
- Faulty reductant quality sensor
- Contaminated diesel exhaust fluid (DEF)
- Wiring or connector issues leading to poor signal
- ECM software glitch
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's not recommended to drive long-term as it could lead to increased emissions and potential damage to the aftertreatment system.
Will this code come back after clearing?
If the underlying issue isn't fixed (sensor or DEF quality), the code will likely return.
Why does this code pair with others like P204B?
These codes represent different issues related to DEF quality and sensor performance; diagnosing one often involves checking others.
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