Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Reductant Quality Module
The reductant quality module provides the reductant tank level and reductant concentration to the PCM. The reductant quality module incorporates an ultrasonic transducer and sensor assembly, located at the bottom of the reductant tank. The transducer produces timed ultrasonic sound waves through the diesel exhaust fluid (DEF) and the sensor measures the return rate of the sound waves. As the DEF is consumed, the liquid level lowers and the return speed increases. Additionally, the sensor monitors reductant concentration percentage by calculating the speed of sound travel through the DEF and comparing it to an expected value. If this value is not met, the reductant is diluted or contaminated. The reductant quality module is integral to the reductant tank assembly.
Typical Reductant Quality Module (All Others)
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.