$1,095
+ $500 refundable core deposit (90-day return window). No-deposit option available at checkout: send your core first.
In stock. Ships today on orders placed by 3 PM Central. Need it tomorrow? Overnight rush is $250 at checkout.
2-year transferable warranty · Programmed to your truck at no charge · Core deposit refunded on return
Failed flash recovery available. Start a repair →
Prefer to fix your own unit?
Flat rebuild $675 (bench fee included) · 15 to 30 days on the bench — you keep your original ECM.
Start a repair instead →
Flat rebuild $675 (bench fee included) · 15 to 30 days on the bench — you keep your original ECM.
Start a repair instead →
| Part Number | 3944125 |
| Brand | Cummins |
| Condition | Remanufactured |
| SKU | NL-CUM-3944125 |
| Warranty | 2-year transferable warranty |
About the Cummins ISC / ISL (CM554) ECM
The 3944125 is the engine control module for the Cummins ISC / ISL (CM554).
These medium-duty ISB and ISC controllers were used from roughly 2003 through the early 2010s in trucks, buses, and diesel-pusher motorhomes.
We repair this ECM on the bench and supply tested, remanufactured exchange units, programmed to your engine and ready to install. This one is on the shelf: order by 3 PM Central and it ships today.
Remanufactured Cummins ISC / ISL ECM, P/N 3944125. Programmed to your CPL #, HP, torque, rear ratio, tire size, and transmission. Plug and play install. Standard programming included — usually ships within 10 business days, often sooner. 2-year warranty. Core exchange required. $500 core deposit refunded when your old ECM returns within 90 days. ECM module family: CM554/CM558.
Common Cummins ECM failures we repair
We fix these on the bench every day. Wiring and connectors can mimic ECM failure, so we test first.
- Injector driver faults. The circuits that fire the injectors burn out or go weak, so the engine misfires, runs rough, or loses a cylinder. We rebuild these driver stages on the bench.
- No communication. The module stops talking to your scan tool over J1939, usually from a failed internal power supply. We track the dead spot and bring it back.
- Heat, vibration, and intrusion damage. Cracked solder joints, blown fuses, and oil or moisture in the board cause faults that come and go. We repair them at the component level and bench-test before it ships.
Repair instead of replace: Cummins ISB and ISC ECM repair →