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Glossary

The shorthand you'll run into around Cummins-powered pickups, trucks and buses, explained in plain words.

6BT / 6BTA ISB 12-valve / 24-valve VE pump P7100 (P-pump) VP44 Common rail (HPCR) CP3 / CP4.2 Lift pump KDP 53 block EGT Boost Wastegate VGT Intercooler HO / SO EGR DPF / regen SCR / DEF NAC APPS Grid heater Fuel dilution TSB Recall ISV5.0 R2.8 B6.7 L9 ISX / X15 X12 MidRange XPI CAPS Single Module aftertreatment ESN Equipment recall Stay Warm

6BT / 6BTA
Cummins' name for the 5.9L 12-valve B-series six. The "A" is commonly read as aftercooled (intercooled).[1,2]
ISB
The electronically controlled B-series Cummins: the 24-valve 5.9 (1998.5 on) and the 6.7. DrivingLine expands it as "Interact System, B series".[3,4]
12-valve / 24-valve
Two or four valves per cylinder on an inline six. 12-valve means the 1989–1998 5.9; "24-valve" usually means the 1998.5–2002 VP44 engine, though all later Cummins in Rams also have 24 valves.[1,3]
VE pump
Bosch VE: a compact, mechanical rotary (distributor) injection pump with a single pumping plunger, used on 1989–1993 5.9 engines.[1,5]
P7100 (P-pump)
Bosch P7100: a large mechanical inline injection pump with one plunger per cylinder, used 1994–1998. Famous for how much fuel it can be made to flow.[2,5]
VP44
Bosch VP44: an electronically controlled rotary pump with three plungers and a built-in control module, used 1998.5–2002. It relies on incoming fuel for cooling.[3,6]
Common rail (HPCR)
A fuel system where a pump keeps a shared rail at very high pressure, and electronically fired injectors decide when and how much to inject. Used from 2003 on.[7,8]
CP3 / CP4.2
Bosch high-pressure common-rail pumps. CP3: 2003–2018 and 2021–2024. CP4.2: 2019–2020 6.7 (recalled; see 21V-880).[7,4,9]
Lift pump
The low-pressure pump that moves fuel from the tank to the injection pump. Mechanical on 12-valves, electric from 1998.5. A weak lift pump can starve and damage a VP44 or CP3.[3,10,7]
KDP
Killer dowel pin: a timing-housing locating pin that can work loose on older 5.9s and fall into the gear train. Usually fixed with a retaining tab.[1,2,10]
53 block
Certain 1999–2001 24-valve blocks with "53" cast in the side, with thinner water jackets that are prone to cracking.[3,11]
EGT
Exhaust gas temperature, read by a pyrometer probe in the exhaust manifold or downpipe. Commonly monitored when towing or running added fuel.
Boost
Intake manifold pressure above atmospheric, made by the turbocharger, usually shown in psi.
Wastegate
A valve that lets exhaust bypass the turbine to limit boost. The HX35W, HY35W, HE341CW and HE351CW are wastegated (the "W").[2,3,7]
VGT
Variable-geometry turbo: movable vanes change exhaust flow over the turbine, so no wastegate is needed. Also lets the 6.7 work as an exhaust brake.[8,10]
Intercooler
Air-to-air heat exchanger that cools the compressed intake charge. Added to the 5.9 in 1991.5.[1]
HO / SO
High Output / standard output. Ram's labels for the higher- and lower-rated engines in a model year.[3,4]
EGR
Exhaust gas recirculation: routes cooled exhaust back into the intake to cut NOx. Used on the 6.7 (not on the 5.9 common-rail in Ram pickups).[7,8]
DPF / regen
Diesel particulate filter, which traps soot, and the regeneration process that burns it off. 6.7 from 2007.5.[8,10]
SCR / DEF
Selective catalytic reduction uses diesel exhaust fluid (a urea solution) to cut NOx. On Ram pickups from 2013.[8,4]
NAC
NOx adsorber catalyst, used on 2007.5–2012 6.7 pickups before SCR.[8,4]
APPS
Accelerator pedal position sensor. A failing one causes "dead pedal" on 1998.5–2004 trucks.[10]
Grid heater
An electric heating grid in the intake used as a cold-start aid on Cummins Rams through 2024; replaced by glow plugs for 2025.[4,12]
Fuel dilution
Diesel fuel getting into the engine oil, mostly from DPF-regeneration strategies on early 6.7s.[4,10]
TSB
Technical service bulletin: a manufacturer's repair guidance to dealers. Not a recall, and not always free. Summaries are searchable on nhtsa.gov.[13]
Recall
A safety campaign the manufacturer must remedy for free. Search by VIN at nhtsa.gov/recalls.[14]
ISV5.0
Cummins' 5.0-liter V8 turbo diesel, used in the 2016–2019 Nissan Titan XD and a few bus and motorhome chassis.[15,16]
R2.8
Cummins' 2.8-liter four-cylinder crate engine, sold as a complete repower kit from 2017.[17,18]
B6.7
The 2017-on name for the commercial 6.7-liter B-series (formerly ISB6.7) used in trucks, buses and RVs.[19,20]
L9
The 2017-on name for the 8.9-liter ISL. Common in transit buses, fire apparatus, motorhomes and heavier medium-duty trucks.[19,21]
ISX / X15
Cummins' 15-liter heavy-duty six. The ISX15 became the X15 for 2017.[22,23]
X12
Cummins' lightweight 12-liter-class heavy-duty engine (about 2,050 lb), successor to the ISX12.[24,25]
MidRange
Cummins' term for its B, C and L series engines (roughly 6.7 to 9 liters) used in medium-duty trucks and buses.[19,26]
XPI
Cummins' extra-high-pressure common-rail fuel system, used on the ISC8.3, ISL9 and ISX15 from 2010 and on today's L9 and X15.[26,27]
CAPS
Cummins Accumulator Pump System, the fuel system the ISL launched with in 1999.[28]
Single Module aftertreatment
Cummins' 2017-on exhaust unit that packs the oxidation catalyst, particulate filter and SCR into one canister.[19,27]
ESN
Engine serial number: Cummins' identifier for an individual engine, generally eight digits, found on the engine dataplate. Engine recalls and service history follow the ESN.[29]
Equipment recall
A recall filed against a part or engine rather than a vehicle. Cummins engine recalls carry an "E" in the NHTSA campaign number (for example 18E-081).[30,14]
Stay Warm
A Cummins engine feature that holds exhaust temperature up so a DPF regeneration can finish in low-speed duty such as school buses.[31,32]

SRCSources

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

  1. DrivingLine Cummins History, Lesson 1: '89-'93 5.9L
  2. DrivingLine Cummins History, Lesson 2: '94-'98 5.9L
  3. DrivingLine Cummins History, Lesson 3: '98.5-'02 5.9L
  4. Diesel Hub 6.7 Cummins Turbodiesel Specs & Info
  5. Diesel Hub 5.9 Cummins 6BT Engine Info (12 Valve)
  6. Green Handle Media 1998.5-2002 5.9L Cummins
  7. DrivingLine Cummins History, Lesson 4: '03-'07 5.9L
  8. DrivingLine Cummins History, Lesson 5: '07.5-'18 6.7L
  9. Diesel World The Recall You Wanted: Cummins CP4
  10. Diesel Hub Common 5.9L & 6.7L Cummins Diesel Problems
  11. Diesel Hub Cummins 53 Block Casting Information
  12. Cummins Inc. Cummins Launches Next Generation 6.7L Turbo Diesel Pickup Engine System for 2025 Ram Heavy Duty Trucks (press release, Jan 7 2025)
  13. NHTSA NHTSA Datasets and APIs (Manufacturer Communications / TSB files)
  14. NHTSA Check for Recalls (VIN and year/make/model search)
  15. Nissan North America (nissannews.com) 2016 Nissan TITAN XD Press Kit (specifications)
  16. Diesel Hub Nissan Titan 5.0 Cummins Engine Information
  17. Cummins Inc. R2.8 Turbo Diesel (product page)
  18. Cummins Inc. Cummins Announces Start of Sales for R2.8 Turbo Diesel Crate Engine (Sep 29, 2017)
  19. OEM Off-Highway (Cummins release) Cummins Introduces B6.7 and L9 Engines at The Work Truck Show 2016 (press release, Mar 2016)
  20. Cummins Inc. B6.7 for Medium-Duty Truck (2021) (product page)
  21. CPTDB Wiki Cummins L9
  22. Engine Builder The Cummins ISX Engine Generates Strength (Jul 2014)
  23. Heavy Duty Trucking (truckinginfo.com) Cummins: New X15 Engine Offers High Performance, Economy, Reliability (2016)
  24. Cummins Inc. X12 (2024) (product page)
  25. Truck News Freightliner 114SD gets Cummins X12 (Dec 11, 2018)
  26. Cummins Inc. (investor news) Cummins Receives EPA 2010 Certification for Heavy-Duty and MidRange Engines (Jan 8, 2010)
  27. Cummins Inc. L9 for Medium-duty (2024) (product page)
  28. Diesel Progress via The Free Library No mistaking new Cummins ISL engine (Diesel Progress, 1998)
  29. Cummins Inc. (QuickServe) Finding your engine serial number (ESN)
  30. NHTSA NHTSA Recalls API, campaignNumber lookup (each campaign below queried 2026-10-19)
  31. School Transportation News Demystifying the Complexity in School Bus Regen Issues (Apr 2019, Thomas Built Buses partner content)
  32. Cummins Inc. DPF Maintenance For Your School Bus (white paper, PDF)