Cleaning a DEF sensor, particularly a DEF quality sensor, typically involves a specific soaking process using fresh Diesel Exhaust Fluid (DEF) itself. This method helps to dissolve any crystallized DEF that may be obstructing the sensor's function, restoring its accuracy.
Understanding DEF Sensor Contamination
Diesel Exhaust Fluid (DEF) contains urea, which can crystallize over time and build up on various components within the Selective Catalytic Reduction (SCR) system, including the DEF sensor. This crystallization can lead to inaccurate readings, system malfunctions, and diagnostic trouble codes, indicating a need for maintenance.
The Recommended Method for Cleaning a DEF Quality Sensor
The most effective and recommended approach to cleaning a DEF quality sensor involves a gentle, chemical-free soaking process. This method leverages the DEF's own properties to dissolve the hardened crystals without damaging the sensor's delicate components.
What You'll Need
Before you begin, gather the following items:
- Known Good DEF Fluid: This is crucial. Use fresh, high-quality DEF that meets ISO 22241 standards.
- Clean Container: A non-metallic container large enough to submerge the sensor end completely.
- Zip Ties: For resecuring the sensor's rubber boot.
- Personal Protective Equipment (PPE): Gloves and eye protection are recommended as DEF can be an irritant.
| Material | Purpose |
|---|---|
| Known Good DEF | Soaking solution to dissolve DEF crystals |
| Clean Container | To hold the DEF and the sensor assembly |
| Zip Ties | To secure the rubber boot after cleaning |
| PPE (Gloves, Eyewear) | For personal safety during handling of DEF |
Step-by-Step Cleaning Process
Follow these steps carefully to clean your DEF quality sensor:
- Remove the Sensor: Safely disconnect and remove the DEF quality sensor assembly from its location on your vehicle's DEF tank. Refer to your vehicle's service manual for specific removal instructions.
- Prepare the Soaking Container: Fill a clean, non-metallic container with fresh, known good DEF fluid. Ensure there is enough fluid to fully submerge the sensor end of the assembly.
- Submerge the Sensor: Carefully place the DEF quality sensor end of the assembly into the container, ensuring it is completely submerged in the DEF fluid.
- Soak Overnight: Allow the sensor to soak in the DEF fluid overnight. This extended soaking period gives the fresh DEF ample time to naturally dissolve any crystallized DEF buildup on the sensor's surface.
- Remove and Inspect: After the overnight soak, remove the sensor from the container. Gently rinse it with clean water (preferably distilled) if any loose debris remains, but avoid harsh scrubbing. Inspect the sensor for any remaining crystallization. If necessary, you may repeat the soaking process.
- Prepare for Reinstallation: Reinstall the rubber boot securely over the sensor. Use zip ties to ensure the boot is tightly fastened, preventing future moisture or debris ingress.
- Reinstall the Sensor: Carefully reinstall the cleaned DEF sensor assembly back into your vehicle's DEF tank, following the manufacturer's torque specifications and procedures.
Why This Method Works
This cleaning method is effective because DEF is primarily composed of urea and deionized water. The fresh DEF in the container acts as a solvent, naturally dissolving the hardened urea crystals that accumulate on the sensor. Unlike harsh chemicals or abrasive cleaning tools, fresh DEF won't damage the sensor's delicate electronic components or its plastic housing.
Important Considerations When Cleaning DEF Sensors
- Avoid Harsh Chemicals: Never use solvents, gasoline, brake cleaner, or other harsh chemicals to clean a DEF sensor. These substances can irreparably damage the sensor and other DEF system components.
- Use Quality DEF: Always use certified DEF that meets ISO 22241 standards. Poor quality DEF can lead to more frequent crystallization and sensor issues.
- Handle with Care: DEF sensors are precision instruments. Handle them carefully during removal, cleaning, and reinstallation to avoid damage.
- When to Replace vs. Clean: While cleaning can resolve many issues, a severely damaged or consistently malfunctioning sensor may need to be replaced. If cleaning doesn't resolve the problem, consult a qualified mechanic.
Preventing Future DEF Sensor Issues
Proactive measures can help extend the life of your DEF sensor and prevent crystallization issues:
- Store DEF Properly: Keep DEF in a cool, dry place, away from direct sunlight, and within the recommended temperature range to prevent degradation and crystallization.
- Use Clean Equipment: Always use clean funnels, nozzles, and containers when refilling your DEF tank to avoid introducing contaminants.
- Don't Overfill: Avoid overfilling the DEF tank, as this can sometimes lead to issues.
- Regular Maintenance: Adhere to your vehicle's recommended service intervals for the DEF system.
By following these guidelines and the specific cleaning method, you can effectively address issues related to a contaminated DEF quality sensor and help maintain the efficiency of your vehicle's emissions system.
