Mack MP8 SPN 1569 FMI 31 �?Engine Protection Torque Derate Active

Code Details

Plain-English Meaning

The Mack MP8 ECM reduces engine power when any critical parameter crosses a protective threshold. SPN 1569 FMI 31 confirms a derate is active, but the companion fault codes identify the root cause. On Mack Anthem, Pinnacle, and Granite trucks with the MP8, SPN 1569 FMI 31 is a critical derate trigger. VCADS Pro displays the inducement counter status and all active fault codes that are contributing to the severe derate condition. The strategy is to identify and resolve all contributing fault codes — DEF quality, SCR efficiency, DPF condition — and then perform the required aftertreatment reset in VCADS Pro to clear the inducement history and lift the derate.

SPN 1569 is the Engine Protection Torque Derate parameter in J1939. FMI 31 indicates the derate is currently active on the Mack MP8 EMS platform. The MP8 shares its protection logic with the Volvo D13 �?common triggers include SCR inducement reaching the derate stage, high coolant temperature, low oil pressure, and critical DPF soot loading.

Common Symptoms

• Noticeable power reduction during operation
• Possible vehicle speed limitation
• Check engine or engine protection warning active on the Mack cluster
• Multiple companion fault codes in Mack service tools
• Very limited vehicle speed — typically 5 mph cap in severe inducement stage
• Multiple aftertreatment fault codes active simultaneously

Possible Causes

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

• SCR or aftertreatment inducement reaching the derate stage
• High coolant temperature from a cooling system fault
• Low engine oil pressure
• DPF critical soot overload
• Multiple simultaneous faults triggering the protection strategy
• Prolonged SCR inefficiency from poor DEF quality or failed dosing injector
• Accumulation of multiple aftertreatment faults without resolution

First Checks

• Connect Mack diagnostic software and review all active fault codes to identify the primary trigger
• Check coolant level, oil level, and DEF quality as quick baseline checks
• Resolve the underlying cause �?SPN 1569 FMI 31 clears when the triggering parameter normalizes
• Connect VCADS Pro and review all active fault codes contributing to the derate
• Address root causes in order: DEF quality first, then dosing system, then SCR catalyst

Can I Keep Driving?

The Mack MP8 is derated while this fault is active. If the trigger is a cooling or lubrication issue, continued operation risks engine damage. If aftertreatment-related, the derate deepens with additional distance.

Related Lookup Pages

• SPN 1569 topic page
• FMI 31 explanation
• Search this code