Thomas lists 200–260 hp for the C2 and 240–300 hp for the HDX2; Blue Bird lists 200–260 hp for the Vision.
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.
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.
1998
Electronic "Interact System" B engine (ISB) arrives; the 5.9 ISB also went into Ram pickups from 1998.5.[9,8]
2007
Cummins Particulate Filter (DPF) added for EPA 2007; school buses got DPFs from around this time.[5,10]
2010
EPA 2010: SCR with diesel exhaust fluid added to cooled EGR and the DPF; ISB6.7 uses a high-pressure common rail and a single VGT.[5,12]
2017
Renamed B6.7 with Single Module aftertreatment (DOC, DPF and SCR in one unit) and new Efficiency/Performance ratings.[1,2]
2024
EPA 2024 certified B6.7 offered for school buses and trucks.[3,4]
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.
DPF regeneration trouble in stop-and-go duty
Applies to DPF-equipped ISB/B6.7 (and ISL/L9), especially school buses
A particulate filter cleans itself by burning off soot, and that needs sustained exhaust heat. School-bus routes, with long idles, light loads and constant stopping, often don't provide it, so active regenerations get interrupted, the DPF lamp comes on and the bus may need a parked regeneration. Thomas Built Buses called it one of the biggest pain points for school-bus fleets.
Cummins' advice is to cut idle time, run about 20 minutes at highway speed and load when the lamp comes on, and use its Stay Warm and idle-shutdown features. Thomas says Stay Warm became a factory-programmed default on Cummins engines with a standard exhaust layout from April 2017.
What to watch for
A DPF lamp that keeps coming back.
Frequent parked or forced regenerations.
Whether Stay Warm and idle shutdown are enabled on older buses.
SCR catalysts that wore out early (2010–2015 emissions recall)
Applies to Model-year 2010–2015 medium- and heavy-duty trucks and buses with Cummins engines
In July 2018 EPA and the California Air Resources Board announced that Cummins would recall about 500,000 model-year 2010–2015 medium- and heavy-duty vehicles because their SCR catalysts degraded within a few years, letting NOx emissions exceed the standards. CARB counted about 60 Cummins engine families, from big rigs to some buses. Both agencies stressed it was a defective part, not a defeat device, and not a safety issue.
This is an emissions recall run under EPA/CARB rules, so it won't appear in NHTSA's safety-recall search. Cummins handled owner notices; CARB said the catalyst replacement is needed to renew California registration for most affected engine families.
What to watch for
Proof the catalyst was replaced on a 2010–2015 vehicle.
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.[35]
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.[25,36]
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: 2019 International MV2016 Thomas Built Buses Saf-T-Liner C2
Safety recalls we verified on NHTSA
Engine ("E") campaigns filed by Cummins Inc. and vehicle ("V") campaigns filed by the bus or truck maker. Several ISB/B6.7 campaigns also cover other Cummins families. 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.
ISB6.7 built Feb 16, 2010 - May 4, 2012 for Thomas Built Buses · Fan drive pulley
A fan pulley problem could let the belt lose the water pump, overheating the engine and possibly disabling the bus. A new fan drive pulley is installed. Thomas Built's matching campaign for non-school buses is 12V-572.[27]
Engine recall (filed by Cummins) · about 7,040 units
B6.7 with fuel module option FS90301 or FS90453 (school buses, trucks, emergency vehicles) · Electric fuel heater
The fuel heater inside the fuel module could overheat, melt its plastic and possibly catch fire, or stall the engine. Dealers fit a redesigned heater. Navistar's matching vehicle recall is 19V-216.[28]
Engine recall (filed by Cummins) · about 68,605 units
A bolt that wasn't tightened enough could let the rear lifting bracket pull away from the cylinder head while the engine is being lifted. Dealers inspect and replace parts as needed.[30]
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.[32]
Engine recall (filed by Cummins) · about 11,860 units
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.[33]
Engine recall (filed by Cummins) · about 805 units
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.[34]
Engine recall (filed by Cummins) · about 12,196 units
07Marine cousins
Cummins also sells B-series engines for boats as the QSB6.7/QSB7, a separate marine product line (230–550 hp) with its own ratings and certification. They aren't covered here.[23,24]
SRCSources
Accessed October 2026. Numbers in brackets throughout the page point here. Brand names are used descriptively.