What This Actuator Does and Where It Lives
This is the Holset VGT actuator - bolts to the turbo housing and drives the unison ring that moves the variable geometry vanes. On the ISX it's how the ECM controls exhaust backpressure for braking and boost, so when it goes flaky you get funky derates, EGT warnings, or the truck just goes into limp mode on a grade.
4034289 is the Cummins part number stamped on the ISX application, and it's the one guys usually read off the old actuator housing when they call in. Common on ISX motors from the mid-2000s through the 2010s in KW, Pete, and Volvo trucks, but 'ISX' covers a lot of ground - always pull the engine serial number off the dataplate before you order.
Why the Cross Numbers Match Up (and Where They Don't)
Holset made this actuator under a handful of numbers - 5501185HX, 6378204H, 6382093RX, 6378270RX - and Cummins re-boxed the same unit as 2837201 and 4032760 depending on which parts catalog era you're in. Different superseding runs, same physical actuator, which is why they cross.
Where it gets sideways is the electrical connector pigtail and the mounting bracket - Holset ran a couple different connector styles over the years, and some ISX applications used a slightly different mounting arm length to match a different turbo casting. If your old actuator has a different plug shape or the arm doesn't line up with the unison ring linkage, it's not this part no matter what the box says.
Surest way to confirm: get the number physically off your old actuator, not just the ECM fault code, and check it against 4034289 or one of the crossed Holset/Cummins numbers before you order. Fault codes tell you the actuator's suspect, not which one you need.
Ordering From PartStop
We keep 4034289 in stock in Tacoma and it usually ships same day if you order before early afternoon. If you're a local fleet running a truck down, call ahead and we'll have it up front for you to grab.
Comes with a 6+ month warranty. This is a $799 part and not something you want to guess on twice, so if you're not 100% sure on the number, snap a picture of the old unit and send it over or give us a call - we'll cross it before you pay for shipping on the wrong actuator.
4034289 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 4034289. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| Holset | 5501185HX, 6378204H, 6382093RX, 6378270RX |
| Cummins | 2837201, 4032760 |
Frequently asked questions
Does 4034289 fit my 2013 Kenworth T680 with ISX15?
Probably, but confirm by the engine serial number on the dataplate, not just the truck model - Cummins ran a few actuator variations across ISX build years. Pull the old actuator's number if it's still legible and match it against 4034289 before ordering.
Is this the same as Holset 6378204H?
Same actuator, yes - 6378204H is one of the Holset numbers that crosses to Cummins 4034289. They're the same physical part under different catalog numbering, just confirm your connector plug matches since Holset changed pigtail style on some production runs.
My actuator isn't throwing a code but the truck derates on hills - is this the part?
Sticking actuators don't always throw a hard code before they get bad enough to affect boost control, especially early on. Have it tested on a bench or at least manually actuate it if you can access it - if it's sluggish or won't hold position, that lines up with this failure.
Not sure it fits? We check before you pay.
Run your VIN and we’ll match parts to your exact truck, or call the counter — a person who knows trucks verifies fitment by OEM number before the order ships. No wrong-box returns.
More cross-reference guides
Need the part, not just the reading?
Every part below is a Premium Quality aftermarket Direct Replacement with published OEM cross-reference numbers, a 6+ month warranty and same-business-day shipping from Tacoma, WA. Not sure it fits? Run your VIN — or call and a person who knows trucks will verify fitment before you pay.