Cummins ISX12 (legacy)
11.90L Inline-6 turbo diesel • Cummins
About the Cummins ISX12 (legacy)
The Cummins ISX12 (11.9L) was Cummins' mid-displacement Class 8 engine from 2010-2018, replacing the older ISM 11L and bridging into what became the X12 in 2019. The ISX12 was popular in regional fleets and vocational applications where the ISX (15L) was too heavy. Production wound down 2018 as the X12 evolved from this platform. Used ISX12 trucks remain common in the secondary market.
Overview
The Cummins ISX12 (11.9L) was Cummins' mid-displacement Class 8 engine from 2010-2018, replacing the older ISM 11L and bridging into what became the X12 in 2019. The ISX12 was popular in regional fleets and vocational applications where the ISX (15L) was too heavy. Production wound down 2018 as the X12 evolved from this platform. Used ISX12 trucks remain common in the secondary market.
Specifications
- Manufacturer
- Cummins
- Displacement
- 11.90 liters
- Configuration
- Inline-6 turbo diesel
- Fuel type
- Diesel
- Horsepower
- 350–500 hp
- Torque
- 1150–1650 lb-ft
- Production years
- 2010–2018
- Truck classes
- Class 8
- Applications
- Regional haul, vocational (legacy)
Design and engineering
11.9L inline-6, parent-bore block, EPA 2010 SCR + DEF compliance.
Generations and emissions eras
Reliability and longevity
Acceptable for the era. DEF/SCR system issues common at 400K+ miles.
Common problems
DEF/SCR failures, NOx sensors, EGR cooler. Parent-bore block limits rebuild options.
Pros and cons
✓ Pros
- • Right-sized for regional/vocational
- • Cummins parts network
⚠ Cons
- • Production ended 2018
- • Replaced by X12
- • DEF system complexity