Cummins ISC ECM Repair Service

The model year will not tell you which Cummins ISC ECM you have

This page is a repair service on the ISC ECM you already own, not a replacement unit. Your module makes the round trip to our facility and returns rebuilt, tested, and still the same module that came off the engine. You order by the part number printed on the module label, because the three numbers in this catalogue overlap on model year. A 2005 ISC sits inside all three bands. A 2002 narrows it to two. The year rarely gets you to a single number, and the label is what decides it.

Three ISC part numbers, and what the certification record shows against each

Diesel ECM Exchange services three ISC part numbers, and EPA annual certification data records each of them against more than one Cummins engine family.

• 3944105 is recorded against ISC and ISL 330/370 ratings, and against the QSC8.3-C, across model years 1998 to 2005.
• 3944125 is recorded against ISC and ISL 310 to 400 ratings, and against QSC and QSL, across model years 2000 to 2010.
• 3965159 is recorded against ISC and ISL 280 to 400 ratings, and against ISB 215, 245 and 260 ratings, across model years 2004 to 2011.

Those model year bands overlap by design of the engine families, not by accident of the catalogue, which is why the number on the label does the work the year cannot. The record itself is published in the EPA's annual certification data for vehicles, engines and equipment.

All three of these numbers also carry ISL ratings, and two of them carry QSC or QSL ratings. This site has no separate ISL, QSC or QSL page, so an owner holding one of these numbers orders it here. A fourth option in the list covers a module whose label cannot be read.

The programming has to store and hold before your module goes back

Diesel ECM Exchange runs board-level rebuilds on diesel engine control modules for owner-operators, fleets and the independent shops that work on them, and every ISC module we take in gets that treatment. We replace and resolder failed components, and we deal with the components that fail most often on these boards whether or not they have gone yet. We then test for communication, confirm the module still takes its programming, and check that the programming and parameters store properly. The unit is fully rebuilt and tested for quality before it ships.

On a repair the free lifetime warranty is in place from the moment your working module goes back to you. Nothing has to be sent in first to activate it, because the module is your own.

What a misread label costs you on each route to a working ISC ECM

On this page it costs nothing. The options for 3944105, 3944125, 3965159 and an unknown number all carry the same price, and the module itself arrives on our bench either way, so what is printed on the label does not change what we do with it.

The outright route runs on the opposite logic. Those same three numbers become separate listings when you buy a rebuilt ISC ECM outright, because a unit has to be built and programmed against one specific number before it can ship. Name the wrong number and the wrong unit arrives. That route also costs more than twice this one, and its lifetime warranty stays dormant until your old one is back with us.

A used or salvage module is the least forgiving of the three routes. Nothing on it has been rebuilt or checked, any cover attached to it is the seller's rather than the product of a rebuild, and a wrong number there is money you will not see again.

Where 3944125 sits between this page and the ISB page

3944125 is orderable here and on the Cummins ISB ECM repair page, at the same price on both. EPA certification data records that number against ISC and ISL ratings rather than ISB, so if 3944125 is what your label shows, this is the page to order it from. The ISB page carries six other numbers from that family and is the one to use if your label shows any of those instead. Both sit under the rest of the Cummins ECM pages.

Before you send your ISC module in

My engine is a Cummins ISL, not an ISC. Am I on the right page?

Yes, if the number on your module label is 3944105, 3944125 or 3965159. EPA annual certification data records all three of those numbers against ISL ratings as well as ISC ratings. There is no separate ISL page on this site, so those numbers are ordered from this one. Go by the number on the label rather than by the badge on the engine.

Could this be a sensor rather than the ECM?

Three patterns tend to sit with the module rather than with a sensor.

• The engine will not start, or it cuts out at random while running.
• A diagnostic scan tool cannot raise the module at all.
• Codes you have already chased by swapping the sensors they name come straight back.

None of the three proves the module on its own, so treat them as narrowing the search rather than ending it.

Does the module need to come off the engine before I place the order?

No. Place the order first. We get in touch afterwards with a pre-paid shipping label, and the module travels once that is in your hands. Pulling it early gains you nothing, because the label only follows the order.

The same three part numbers are on another of your pages at more than twice the price. What is different?

That page hands you a rebuilt module to fit, instead of working on the one already in your truck. Your existing unit stays out of the job entirely and a different one goes in. This page takes in the module you have and sends that same one back. Neither page is a premium version of the other. They are two routes to a working ECM, suited to different situations.

How long is my module on your bench?

Bench time runs 3 to 5 business days, counted from the day your core lands at our facility. Transit in both directions sits on top of that and is not counted inside the window. The count starts on arrival rather than at checkout, so a module posted on a Friday begins its window the day it reaches us.

My label shows a number that is not among the three. What do I order?

Pick the option for an unknown part number. It carries the same price as the options for 3944105, 3944125 and 3965159. Certification records also list ISC family numbers that this catalogue never carried, which is why that fourth option is there.