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Detroit Diesel SPN 3031 FMI 1 indicates that the Diesel Exhaust Fluid (DEF) tank temperature has dropped below the acceptable operating range. This code is most commonly seen on DD13, DD15, and DD16 engines during cold weather operation and can affect DEF flow and SCR system performance.
Symptoms
- Check engine light on
- DEF system warning light illuminated
- Reduced SCR system performance
- Possible engine derate in severe cases
Cause
DEF freezes at 12°F (-11°C). This code triggers when the DEF tank temperature sensor detects fluid that is too cold to flow properly through the dosing system. Common causes include:
- Extreme cold weather operation
- Faulty DEF tank heater
- Failed DEF temperature sensor
- Broken or disconnected heater wiring
Can You Keep Driving?
Short distances may be possible but if the DEF system cannot supply fluid to the SCR system due to frozen or cold DEF, a derate condition can follow. In very cold conditions address this before operating the vehicle.
Recommended Action
Allow the vehicle to warm up so the DEF tank heater can bring fluid to operating temperature. If the code persists in normal temperatures, inspect the DEF tank heater, temperature sensor, and associated wiring for faults.
It means the DEF tank temperature has dropped below the minimum operating threshold, which can prevent proper DEF flow to the SCR system.
Most commonly cold weather causing DEF to freeze or become too cold to flow. It can also be caused by a failed DEF tank heater or a faulty temperature sensor.
Limited driving may be possible but if the DEF system cannot function properly due to temperature, a derate condition may follow.
It can if the SCR system is unable to dose DEF properly as a result of the low temperature condition.
Allow the vehicle to warm up fully. If the code clears once the DEF reaches operating temperature, no further action is needed. If it persists, inspect the DEF heater system and temperature sensor.
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.