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Detroit Diesel SPN 3031 FMI 16 indicates that the DEF tank temperature has risen above the acceptable operating range. This code appears on DD13, DD15, and DD16 engines and is important to address promptly as excessive heat can degrade DEF fluid quality, damage the DEF tank and components, and affect SCR system performance.
Symptoms
- Check engine light on
- DEF or SCR warning light illuminated
- DEF fluid may degrade faster than normal
- SCR system performance may be affected
- Engine derate possible if DEF quality is compromised
Cause
This code triggers when the DEF tank temperature sensor detects fluid above the maximum acceptable threshold. Common causes include:
- Faulty DEF tank cooling system
- DEF tank heater stuck in the on position
- Excessive heat exposure from nearby exhaust components
- Faulty DEF temperature sensor giving false high readings
- Operating in extremely high ambient temperatures
- Blocked or restricted DEF tank cooling lines
Can You Keep Driving?
Short distances may be possible but prolonged exposure to high temperatures will degrade DEF fluid quality and can damage the tank and dosing components. If DEF quality becomes compromised a derate condition will follow. Address this fault promptly.
Recommended Action
Check the DEF tank heater to ensure it is not stuck in the on position. Inspect the DEF tank cooling system and lines for blockages or failures. If the temperature reading seems inconsistent with conditions, have the DEF temperature sensor tested. Allow the system to cool and recheck before continuing operation.
It means the DEF tank temperature has risen above the acceptable operating range, which can degrade DEF fluid quality and affect SCR system performance.
The most common causes are a DEF tank heater stuck on, a failed cooling system for the DEF tank, excessive heat from nearby exhaust components, or a faulty DEF temperature sensor.
Short distances may be possible but continued operation with high DEF tank temperature risks degrading the fluid and damaging dosing components, which can lead to further faults and derate.
It can if the high temperature condition degrades DEF quality to the point where the SCR system can no longer meet emissions thresholds.
Identify and fix the heat source — check the DEF tank heater, cooling lines, and temperature sensor. Once the tank temperature returns to the acceptable range and the sensor confirms normal readings the code should clear.
Related codes
Need Immediate Help With This Fault Code?
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Important Notice
The information provided above is for general informational purposes only and should not replace official OEM service procedures. Always consult the manufacturer’s service manual or a qualified diesel technician before performing repairs. Operating a vehicle with active fault codes may result in further damage.