SPN 1569 DTC Explain and Troubleshooting

SPN 1569 FMI 31 is a diagnostic trouble code for engine protection torque derate.

FMI 31 – Engine Protection Torque Derate Condition Exists

DEF sensors and line, update ECM


  • Safety first: Before working on your vehicle, ensure it is parked on a level surface and the engine is off. Wear appropriate personal protective equipment, and disconnect the negative battery terminal to prevent electrical hazards.
  • Check for other related codes: Use a diagnostic scan tool to read any additional fault codes stored in the ECM. This will help you identify if there are other issues contributing to the engine derate condition.
  • Inspect the DEF system: Visually inspect the Diesel Exhaust Fluid (DEF) tank, lines, and dosing unit for any signs of damage, leaks, or blockages. Ensure the DEF tank is filled with the correct fluid, and that the fluid is not contaminated or expired.
  • Check the SCR system: Inspect the Selective Catalytic Reduction (SCR) system, including the SCR catalyst, NOx sensors, and temperature sensors. Look for signs of damage, corrosion, or soot buildup.
  • Inspect the Exhaust Gas Recirculation (EGR) system: Check the EGR valve and cooler for any signs of excessive carbon buildup, leaks, or damage. A malfunctioning system can contribute to the engine derate condition.
  • Check the Diesel Particulate Filter (DPF): Inspect the DPF for excessive soot buildup, cracks, or damage. A clogged or damaged DPF can lead to increased exhaust backpressure and trigger a derate condition.
  • Perform a forced regeneration: If the aftertreatment system components appear to be in good condition, perform a forced regeneration using a diagnostic scan tool. This will help clear any soot buildup in the DPF and allow the SCR system to operate more efficiently.
  • Clear the fault codes: After addressing any issues found during the inspection, use the diagnostic scan tool to clear the stored fault codes.



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