Cummins SPN 1569 FMI 31 – Engine Protection Torque Derate Active

Code Details

Plain-English Meaning

Cummins engines monitor dozens of parameters: coolant temperature, oil pressure, intake manifold temperature, turbo boost, and others. When any of those exceeds the threshold where the ECM believes continued full-load operation could damage the engine, it pulls torque back — sometimes significantly. SPN 1569 FMI 31 is the notification that the derate is happening right now. The driver typically notices it as sudden power loss, sluggish acceleration, or inability to maintain speed on a grade.

SPN 1569 is the J1939 parameter for Engine Protection Torque Derate. FMI 31 means the condition exists — the derate is active. This code functions as a secondary fault alongside the primary fault that caused the protection to trigger. Common primary faults that activate engine protection include: SPN 110 (coolant temperature), SPN 100 (oil pressure), SPN 102 (intake manifold pressure), SPN 174 (fuel temperature), and others. The derate magnitude depends on which parameter exceeded its limit and by how much.

Common Symptoms

• Sudden, noticeable power reduction — often feels like the engine is being held back
• Red or amber warning lamp active
• Engine may idle normally but lack power under load
• Other active fault codes almost always present alongside SPN 1569

Possible Causes

Possible causes may include the items below. The list is not a parts diagnosis.

• Coolant temperature above normal — low coolant level, failed thermostat, clogged radiator, or failed water pump
• Low oil pressure — low oil level, worn oil pump, clogged oil cooler or filter, or oil dilution
• Intake manifold temperature too high — common with a failing charge air cooler or restriction in the intake system
• High fuel temperature — clogged fuel cooler or high return fuel temperature in hot ambient conditions
• Turbocharger issues affecting boost pressure or causing over-boost

First Checks

• Read all active fault codes immediately — SPN 1569 is a consequence; the primary code points to the actual problem
• Check coolant level and temperature before dismissing a heat-related cause
• Verify engine oil level and look for signs of oil contamination or foam (coolant intrusion)
• Check the dash warning lamps: a red stop lamp alongside SPN 1569 indicates a more severe condition than an amber warning lamp
• Do not clear codes before documenting them — the full code set helps the shop identify whether protection is from a single failed component or multiple overlapping conditions

Can I Keep Driving?

If this code is active alongside a red stop lamp, pull over safely and shut the engine down as soon as it is safe to do so — continued operation under those conditions risks significant engine damage. With an amber warning lamp only, the truck may be driveable to a service location at reduced power, but the root cause should be diagnosed promptly.

Related Lookup Pages

• SPN 1569 topic page
• FMI 31 explanation
• Cummins manufacturer hub
• Search this code