$1,095
+ $500 refundable core deposit (90-day return window). No-deposit option available at checkout: send your core first.
Usually ships same day on orders in by 2 PM CT
2-year transferable warranty · Programmed to your truck at no charge · Core deposit refunded on return
Prefer to fix your own unit?
Flat rebuild $675 (bench fee included) · 3-day turnaround — you keep your original ECM.
Start a repair instead →
Flat rebuild $675 (bench fee included) · 3-day turnaround — you keep your original ECM.
Start a repair instead →
| Part Number | 3684009 |
| Brand | Cummins |
| Condition | Remanufactured |
| SKU | NL-CUM-3684009 |
About the Cummins ISX (CM870) ECM
The 3684009 is the engine control module for the Cummins ISX (CM870).
This is an EGR-era big-bore ISX controller, with the CM870 used from roughly 2003 to 2007, the CM871 from roughly 2007 to 2010, and the CM2250 that followed into the early 2010s.
We repair this ECM on the bench and stock tested, remanufactured exchange units, programmed to your engine and ready to install. Send yours in for repair, or buy an exchange unit off the shelf.
Remanufactured Cummins ISX ECM, P/N 3684009. Programmed to your CPL #, HP, torque, rear ratio, tire size, and transmission. Plug and play install. Standard programming included — usually ships same day on orders in by 2 PM CT. 2-year warranty. Core exchange required. $500 core deposit refunded when your old ECM returns within 90 days. ECM module family: CM870.
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.