How to Reset the DEF Level Sensor on a Paccar MX-13
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If your Paccar MX-13 is showing a DEF level warning even after refilling, chances are the DEF level sensor is stuck or out of sync. This is a common issue—and one that can lead to derate if ignored.
Here’s how to reset or recalibrate the DEF sensor using a diesel laptop.
🛠 What You’ll Need:
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Our Diesel laptop that supports Paccar engines
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RP1210 adapter (like Nexiq USB-Link 2 or 3)
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Truck parked with ignition on, engine off
🔄 Step-by-Step: Reset DEF Level Sensor on MX-13
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Plug in your adapter and launch your diagnostic software
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Connect to the MX-13 engine ECM
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Go to Aftertreatment System > DEF Tank Level Sensor
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Select “Relearn” or “Calibrate DEF Level Sensor”
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Follow on-screen instructions:
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Make sure DEF tank is at least ¾ full
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Confirm no active DEF system faults
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Click Start and let the recalibration process complete (2–5 minutes)
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Power cycle the ignition and confirm warning is cleared
⚠️ If It Still Won’t Reset:
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Check for DEF contamination
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Inspect the DEF quality sensor
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Look for SPN 1761, SPN 3364, or SPN 5246 codes
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You may need to replace the tank module if the sensor fails calibration
💡 Pro Tip:
Many shops charge $300+ for this reset alone. A diesel laptop gives you that power anytime, anywhere—especially when paired with regen and code clearing capabilities.
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