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ISM / ISX / X15 / X12 / Heavy duty

Cummins ISM, ISX, X15 & X12 (heavy duty)

Cummins' big-bore engines for Class 8 trucks, coaches, fire apparatus and big motorhomes.

Layout
Inline-6
Displacement
10.8 L (ISM), 11.9 L (ISX11.9/12), 15 L (ISX15/X15)
Fuel system
XPI common rail from 2010
Camshafts
ISX dual cam until 2010, single after
X15 ratings
400–605 hp / 1,450–2,050 lb‑ft
Emissions
EGR + DPF + SCR (2010-on)

01Verified specs

Each row is confirmed in the cited sources. Where they disagree, or only one source has it, the row says so.

ISM displacement10.8 L (the "11-liter" class)[1,4]
ISX / ISX15 / X15 displacement15 L class[2,10]
ISX11.9 / ISX12 displacement11.9 L[5,1]Introduced in 2010 as the ISM's replacement; later called ISX12.
X12 displacement11.8 L[15]Western Star's figure; Cummins markets it as its 12-liter.
X12 weight2,050 lb[12,14]
ISX camshaftsDual overhead cam until 2010; single cam from the 2010 ISX15[2,7]The 2010 change came with the XPI common-rail fuel system.
Fuel system (2010-on)Cummins XPI high-pressure common rail[7,10]
Turbocharger (current)Cummins VGT[7,10]

02Ratings & ranges

Class 8 ratings are chosen when the truck is spec'd; the dataplate and ECM show what a given engine carries.

WhenEngine / applicationPowerTorqueSrc
2010ISX11.9310–450 hp1,150–1,650 lb-ft[5,6]
Concrete Products' March 2009 report on the unveiling quoted 310–425 hp; FleetOwner's 2010 certification report gives 310–450 hp and the torque range. Range shown is the wider one; torque is from FleetOwner only.
2017X15 Performance series485–605 hp1,650–2,050 lb-ft[8,9]
2017X15 Efficiency series400–500 hpup to 1,850 lb-ft[8,9]
2024X15 Productivity series430–605 hp1,650–2,050 lb-ft[10,17]
2024X15 Efficiency series400–500 hp1,450–1,850 lb-ft[11]
2024X12350–500 hp1,250–1,700 lb-ft[12,15,14]

03Where you'll find it

Makes and models we could tie to this engine family through the vehicle maker's own literature and/or NHTSA recall filings. "Years documented" means the years those sources cover. It isn't a complete production span, and not every vehicle of that model has this engine.

VehicleTypeYears documentedEngineSrc
Freightliner CascadiaHeavy truck2016–2019, 2021–2022, 2025 in NHTSA recordsISX15 / X15[16,38,24,39,40]
Freightliner 122SDHeavy truck2016–2019 in NHTSA recordsISX15 / X15[16,38,41,24]
Freightliner 114SDHeavy truckX12 orderable from Dec 2018; production from mid-2019X12[13,14,16]
Western Star 4900 / 6900 / 4700Heavy truck2016–2019 in NHTSA recordsISX12 / ISX15 / X15[16,38,41,24]
Western Star 49XHeavy truck2025 in NHTSA records; currentX12 / X15[15,16,40]
Kenworth T680, T880, W900, W990, C500, T800Heavy truck2017, 2021–2022, 2025 in NHTSA recordsISX12 / ISX15 / X15[16,42,43,27]
Peterbilt 579, 567, 389, 367 (589 in 2025)Heavy truck2017, 2021–2022, 2025 in NHTSA recordsISX12 / ISX15 / X15[16,42,43,27]
International LT, HX, LoneStar (ProStar, 9900i, PayStar earlier)Heavy truck2017–2019, 2025 in NHTSA recordsISX15 / X15[16,44,45]
Volvo VNLHeavy truck2016–2019, 2022 in NHTSA recordsISX12 / ISX15 / X15[16,46,47,48]
Cummins' availability list (last updated Aug 2022) includes VNL and VNX models; check current availability with a dealer.
MCI J4500, D45 CRT LE, D4500 and othersCoach2019–2022 in NHTSA records; current brochuresX12[18,19,33]
MCI brochures list a 410 hp / 1,450 lb‑ft X12 as standard.
Freightliner Custom Chassis XCM / XCPRV chassis2017–2018, 2025 in NHTSA recordsISX15 / X15[41,40]
E-ONE Typhoon, Cyclone, Quest; PierceFire apparatus2013–2019 (E-ONE), 2008–2009 (Pierce) in NHTSA recordsISX12/X12, ISX15/X15, ISM[49,50,17]

See every family side by side on the By vehicle page.

04Emissions eras (EGR, DPF, SCR)

Era dates are Cummins' on-highway emissions steps in North America. A given truck or bus can carry an engine built to the previous standard for a while after a change, so go by the engine dataplate, not just the model year.

  1. 1998

    ISM (from the M11) and the ISX (developed from the 1997 Signature 600) join the Interact System lineup. Sources put first ISX production in 1998 or mid-1999.[1,2,3,4]

  2. 2002

    Cooled EGR and a variable-geometry turbo added on the ISM for the 2002 emissions step (one source; we couldn't confirm the same date for the ISX in a second source).[1]

  3. 2007

    Cummins Particulate Filter (DPF) added for EPA 2007.[7,1]

  4. 2010

    EPA 2010: SCR/DEF, XPI common rail and single-cam ISX15. ISM retired from North American on-highway use in 2010, replaced by the ISX11.9.[7,5,6,1]

  5. 2017–2018

    X15 replaces the ISX15 (limited production fall 2016, full production January 2017); X12 follows to supersede the ISX12.[8,9]

  6. 2024

    EPA 2024 X15 and X12. Cummins now also lists an EPA 2027 X15 and an X10 for fire apparatus.[10,12,17]

05Common issues, in plain English

Patterns documented by the sources below, not a prediction for any one engine. Diagnose before buying parts and follow the engine and vehicle makers' service information.

Fuel-system failures behind several big campaigns

Applies to ISX15 and X15

The largest documented ISX15/X15 problems are in the fuel system. In 2018 Cummins recalled about 91,000 ISX15 and X15 engines because a clogged screen in the fuel pump's cooling circuit could make the nylon fuel line burst on long downgrades; the fix was a steel line. Separate campaigns covered a fuel pump drive gear that could slip (2017) and fuel pump barrels that could fracture (2024).

Each campaign was echoed by the truck makers (Freightliner, Western Star, International, Volvo, Kenworth and Peterbilt), so the same truck may show both a vehicle and an engine campaign.

What to watch for

  • Fuel smell or leaks after long grades.
  • Open campaigns on both the VIN and the engine serial number.

Sources [23,24,25,26,27]

2010–2015 SCR catalyst emissions recall

Applies to Model-year 2010–2015 heavy trucks with Cummins engines

The 2018 emissions recall for SCR catalysts that wore out early covered big rigs as well as medium-duty trucks and buses: about 500,000 vehicles and some 60 engine families. It's an EPA/CARB emissions recall, so it won't show in NHTSA's safety search; Cummins sent owner notices.

What to watch for

  • Records showing the catalyst replacement on a 2010–2015 truck.

Sources [20,21]

ECM short circuits that stall the engine

Applies to ISX12/ISX15 (2015–2016), X15/X12 (2022)

Three campaigns (2015, 2016 and 2022) replaced engine control modules that could short internally, blowing a fuse or stalling the engine, sometimes with no restart until the module was replaced.

Sources [28,29,30]

06Recalls & how to look them up

1. Search the vehicle. Enter the 17-character VIN at nhtsa.gov/recalls. That finds recalls filed by the vehicle maker (the truck, bus or chassis builder), such as Freightliner, Blue Bird or Nissan.[36]

2. Search the engine. Recalls Cummins files against its engines are equipment recalls. Their campaign numbers contain an "E" (for example 18E-081) and they follow the engine serial number (ESN), so they may not show up in a VIN search. On the same NHTSA page, search equipment/manufacturer for Cummins, or open a campaign number directly, then compare its build dates and part numbers with your engine. For a definite answer, give the ESN from the engine dataplate to a Cummins-authorized service location.[22,37]

3. Bulletins. TSBs for medium- and heavy-duty vehicles appear on NHTSA as manufacturer communications when the maker files them; we don't copy their text. Year/make/model shortcuts: 2018 Freightliner Cascadia 2022 Kenworth T680

Safety recalls we verified on NHTSA

Engine campaigns filed by Cummins. The truck-maker versions are named in each summary and linked from the application table. Each one was confirmed in NHTSA's campaign records on 2026-10-19; summaries are in our own words. It's not a complete list for any vehicle.

  • 18E-081

    ISX15 and X15 engines with nylon fuel lines · Fuel pump cooling line

    Debris could clog a screen in the fuel pump cooling circuit until the nylon fuel line burst, typically on long downhill grades, dumping fuel on the road and possibly stalling the engine. The nylon line is replaced with steel. Truck-maker versions include 18V-581 (Freightliner/Western Star), 18V-588 (International) and 18V-668 (Volvo).[23]

    Engine recall (filed by Cummins) · about 91,286 units

  • 17E-029

    Certain X15 engines (trucks, fire trucks, RVs) · Fuel pump drive gear

    The fuel pump drive gear could slip on its shaft and the pump would stop working, stalling the engine. Dealers replace the pump. A related ISX15 vehicle campaign is 17V-450.[25]

    Engine recall (filed by Cummins) · about 2,807 units

  • 24E-078

    Certain X15 engines, reman engines and fuel pump service parts · Fuel pump barrels

    Fuel pump barrels can fracture, leaking fuel and stalling the engine. Cummins replaces the barrels. Truck-maker versions include 24V-789 (Kenworth/Peterbilt), 24V-734 (International) and 24V-736 (Freightliner/Western Star/Freightliner Custom Chassis).[26]

    Engine recall (filed by Cummins) · about 9,332 units

  • 21E-009

    Certain X15 engines · Flywheel capscrews

    Flywheel-to-crankshaft capscrews might be under-torqued, so the flywheel could come loose. Dealers re-torque, inspect and repair. Truck-maker versions: 21V-073 (Freightliner), 21V-080 (Kenworth/Peterbilt), 21V-065 (Volvo).[31]

    Engine recall (filed by Cummins) · about 251 units

  • 21E-099

    Certain X12 engines · Fuel tubes, cylinders 4–6

    High-pressure fuel tubes between the rail and injectors 4, 5 and 6 can fatigue and crack, a fire risk. Low-mileage engines get vibration isolators; others get new tubes with isolators. Motor Coach Industries' coach version is 21V-971.[32]

    Engine recall (filed by Cummins) · about 10,938 units

  • 21V-971

    2019–2022 MCI D4000 ISTV/D4500/D45 CRT LE, 2019–2021 J4500 and others with X12 · X12 fuel tubes

    Coach-maker side of 21E-099: cracked fuel tubes can leak high-pressure fuel.[33]

    Vehicle recall (filed by Motor Coach Industries) · about 1,125 units

  • 16E-047

    ISX12 and ISX15 built Mar 7 - Apr 12, 2016 · Engine control module

    Another ECM short-circuit campaign: a blown fuse stalls the engine and it can't restart until the ECM and fuse are replaced. Truck-maker counterparts include 16V-393 (Volvo) and 16V-426 (Kenworth/Peterbilt).[29]

    Engine recall (filed by Cummins) · about 5,430 units

  • 15E-073

    Certain ISB6.7, ISL9, ISX12 and ISX15 engines · Engine control module

    The ECM could short and blow a fuse, stalling the engine without warning. Dealers replace the ECM. Freightliner/Western Star/Thomas counterpart: 15V-620.[28]

    Engine recall (filed by Cummins) · about 805 units

  • 22E-063

    Certain X15, X12, L9 and B6.7 engines · Engine control module

    An internal short in the ECM can stall the engine. Dealers replace the ECM. Thomas Built's school-bus counterpart is 22V-553.[30]

    Engine recall (filed by Cummins) · about 12,196 units

  • 11E-031

    ISB6.7, ISC8.3, ISL9, ISX11.9 and ISX15 shipped Sep - Dec 2010 · DOC/DPF V-band clamps

    Clamps joining the inlet and outlet sections of the oxidation catalyst/particulate filter could let go and vent hot exhaust early, a fire risk. Cummins worked through the vehicle makers to reach owners.[34]

    Engine recall (filed by Cummins) · about 11,860 units

  • 21E-032

    Certain L9 and ISX12 engines · High-pressure fuel rail

    A sealing washer might not seat in its bore, letting the high-pressure fuel rail leak, which is a fire risk. Dealers inspect threads and lines and replace the rail as needed.[35]

    Engine recall (filed by Cummins) · about 45,334 units

SRCSources

Accessed October 2026. Numbers in brackets throughout the page point here. Brand names are used descriptively.

  1. CPTDB Wiki Cummins ISM
  2. Engine Builder The Cummins ISX Engine Generates Strength (Jul 2014)
  3. FleetOwner Cummins introduces Signature 600 engine
  4. Diesel Progress via The Free Library No mistaking new Cummins ISL engine (Diesel Progress, 1998)
  5. FleetOwner Cummins ISX11.9 certified for 2010
  6. Concrete Products Cummins Unveils The ISX11.9 Engine, ISM's 2010 Successor (Mar 18, 2009)
  7. Cummins Inc. (investor news) Cummins Receives EPA 2010 Certification for Heavy-Duty and MidRange Engines (Jan 8, 2010)
  8. Cummins Inc. Industry Wowed by 2017 X15 Heavy-Duty Truck Engines (Aug 18, 2016)
  9. Heavy Duty Trucking (truckinginfo.com) Cummins: New X15 Engine Offers High Performance, Economy, Reliability (2016)
  10. Cummins Inc. X15 Productivity Series (2024) (product page)
  11. Cummins Inc. X15 Efficiency Series (2024) (product page)
  12. Cummins Inc. X12 (2024) (product page)
  13. Cummins Inc. (investor news) Lightest and Most Productive Class 8 Engine is Available in Freightliner Chassis (Dec 10, 2018)
  14. Truck News Freightliner 114SD gets Cummins X12 (Dec 11, 2018)
  15. Western Star Trucks 49X Powertrains
  16. Cummins Inc. Heavy-Duty Trucks Available with Cummins Engines (last updated Aug 2022)
  17. Cummins Inc. Fire and Emergency engines
  18. Motor Coach Industries MCI J-Series brochure (PDF)
  19. Motor Coach Industries MCI D45 CRT LE brochure (PDF)
  20. U.S. EPA EPA Announces Largest Voluntary Recall of Medium- and Heavy-Duty Trucks (Jul 31, 2018)
  21. California Air Resources Board CARB investigation leads to nationwide recall of 500,000+ Cummins heavy-duty trucks (Jul 31, 2018)
  22. NHTSA NHTSA Recalls API, campaignNumber lookup (each campaign below queried 2026-10-19)
  23. NHTSA (filed by Cummins Inc.) Recall 18E-081 record: ISX15 and X15 engines with nylon fuel lines
  24. NHTSA Recall 18V-581 record: 2017-2019 Freightliner Cascadia, Coronado, 122SD and Western Star 4900 with ISX15/X15 (fuel line)
  25. NHTSA (filed by Cummins Inc.) Recall 17E-029 record: Certain X15 engines (trucks, fire trucks, RVs)
  26. NHTSA (filed by Cummins Inc.) Recall 24E-078 record: Certain X15 engines, reman engines and fuel pump service parts
  27. NHTSA Recall 24V-789 record: 2025 Kenworth C500/T680/T800/T880/W900/W990 and Peterbilt 567/579/589 with Cummins X15 (fuel pump barrels)
  28. NHTSA (filed by Cummins Inc.) Recall 15E-073 record: Certain ISB6.7, ISL9, ISX12 and ISX15 engines
  29. NHTSA (filed by Cummins Inc.) Recall 16E-047 record: ISX12 and ISX15 built Mar 7 - Apr 12, 2016
  30. NHTSA (filed by Cummins Inc.) Recall 22E-063 record: Certain X15, X12, L9 and B6.7 engines
  31. NHTSA (filed by Cummins Inc.) Recall 21E-009 record: Certain X15 engines
  32. NHTSA (filed by Cummins Inc.) Recall 21E-099 record: Certain X12 engines
  33. NHTSA (filed by Motor Coach Industries) Recall 21V-971 record: 2019-2022 MCI D4000 ISTV/D4500/D45 CRT LE, 2019-2021 J4500 and others with X12
  34. NHTSA (filed by Cummins Inc.) Recall 11E-031 record: ISB6.7, ISC8.3, ISL9, ISX11.9 and ISX15 shipped Sep - Dec 2010
  35. NHTSA (filed by Cummins Inc.) Recall 21E-032 record: Certain L9 and ISX12 engines
  36. NHTSA Check for Recalls (VIN and year/make/model search)
  37. Cummins Inc. (QuickServe) Finding your engine serial number (ESN)
  38. NHTSA Recall 15V-620 record: 2016 Freightliner Cascadia, M2, 108SD/114SD/122SD, Western Star 4700/4900, Thomas C2 with ISB6.7/ISL9/ISX12/ISX15 (ECM)
  39. NHTSA Recall 21V-073 record: 2021-2022 Freightliner Cascadia with Cummins X15 (flywheel capscrews)
  40. NHTSA Recall 24V-736 record: 2025 Freightliner Cascadia, Western Star 49X, FCCC XCM/XCP with Cummins fuel pumps (fuel pump barrels)
  41. NHTSA Recall 17V-450 record: 2017-2018 Freightliner 122SD, Western Star 4900/6900, FCCC XCM/XCP with Cummins ISX15 (fuel pump)
  42. NHTSA Recall 16V-426 record: 2017 Kenworth and Peterbilt with Cummins ISX12 or ISX15 (ECM)
  43. NHTSA Recall 21V-080 record: 2021-2022 Kenworth T680/T800/T880/W900/W990 and Peterbilt 367/389/567/579 with Cummins X15 (flywheel)
  44. NHTSA Recall 18V-588 record: 2017-2019 International ProStar, 9900i, LT, LoneStar, HX, PayStar with ISX15/X15 (fuel line)
  45. NHTSA Recall 24V-734 record: 2025 International HX and LT with Cummins X15 (fuel pump barrels)
  46. NHTSA Recall 16V-393 record: 2017 Volvo VNL with Cummins ISX12 or ISX15 (ECM)
  47. NHTSA Recall 18V-668 record: 2016-2019 Volvo VNL with Cummins ISX15 (fuel line)
  48. NHTSA Recall 21V-065 record: 2022 Volvo VNL with Cummins X15 (flywheel capscrews)
  49. NHTSA Recall 19V-730 record: 2013-2019 E-ONE Typhoon, Cyclone and Quest with Cummins ISL, L9, ISX12, X12, ISX15 or X15 (starter circuit)
  50. NHTSA Recall 09V-389 record: 2008-2009 Pierce fire trucks with Cummins ISB, ISC, ISL, ISM and ISX (exhaust/regen switch)