240-5303 10R-3571 Engine Control Module ECM for Caterpillar 3126 3126B 3126E Truck
Remanufactured 240-5303 engine control module (ECM), dedicated to the Caterpillar 3126, 3126B and 3126E engine family.
- Interchangeability: 240-5303 / 2405303 / 10R-3571 / 10R3571
- Application: 3126, 3126B and 3126E truck engines; 3126B marine engines
- Condition: Remanufactured from a tested core, rebuilt at component level and bench-tested
- Programming Required: Module must be flashed to your engine serial number — send us your ESN, VIN and data plate photo after purchase
$1,299.00
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Bench-Tested - Every unit powered up and function-tested before dispatch.
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6-Month Warranty - From delivery, against defects in materials and workmanship.
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30-Day Returns - Unused items in original packaging. RMA required.
Product Details
This remanufactured Electronic Engine Control Module (ECM / ECU) is an aftermarket replacement for Caterpillar part numbers 240-5303 and 10R-3571, dedicated to the 3126 engine family — 3126, 3126B and 3126E truck engines and 3126B marine engines.
The 3126 has been in service a long time. It powers medium-duty vocational trucks, buses, fire apparatus and boats that in many cases are now well past twenty years old, with engines that are mechanically sound but running control electronics of the same vintage. That is the situation this module is usually bought for: the truck is worth keeping, the engine has life left in it, and the ECM has become the thing standing between the two.
Each unit begins as a tested core and is rebuilt at component level. The board is cleaned and inspected under magnification, with capacitors, injector driver components and solder joints renewed wherever measurement calls for it — on modules of this age, electrolytic capacitor drift and fatigued solder joints are the two findings that come up most often. Housing seals and gaskets are replaced, conformal coating is refreshed, and the finished module is bench-tested under simulated load so it will restore factory-specified operating parameters once programmed to your engine.
- Direct replacement fitment — original mounting pattern, connector layout and harness routing, so no wiring modification or bracket fabrication is required.
- Dedicated to the 3126 family — not a broad multi-engine reference, which makes identification simpler if your engine is a 3126, 3126B or 3126E.
- Component-level remanufacture — rebuilt from a tested core with renewed electronics, refreshed conformal coating and resealed housing.
- Age-appropriate rebuild focus — capacitors and solder joints are the primary wear items on modules of this generation, and both are addressed rather than left in place.
- Truck and marine coverage — 3126, 3126B and 3126E on-highway truck engines plus 3126B marine installations.
- Function-restoring, not performance-altering — supplied to restore original operating parameters; no calibration changes of any kind are made to the unit.
- 6-month warranty — repair or replacement service if any fault appears within the period.
Important: Programming Is Required Before Use
This module is not plug-and-play. Every engine carries its own calibration file, and the unit must be flashed to your specific serial number by a qualified technician using approved diagnostic software before the engine will run correctly. On a 3126 this also means the rating and application settings must match your vehicle, since the same engine family was supplied in several power ratings.
Please send us the following after purchase:
- Engine Serial Number (ESN) and Vehicle Identification Number (VIN)
- Clear photographs of your current ECM / ECU unit
- A clear photograph of the engine data plate
Installation and removal of an engine control module should always be carried out by an experienced technician. Disconnect the battery before any work begins.
Fitment & OEM Interchange
The following reference numbers are listed for cross-reference and identification purposes only. All trademarks belong to their respective owners.
| Primary Reference Number | 240-5303 / 2405303 |
| Alternate Reference Number | 10R-3571 / 10R3571 |
| Engine Family | Fits for Caterpillar 3126, 3126B, 3126E |
| Condition | Remanufactured — rebuilt from a tested core |
| Installation | Direct replacement — programming required |
Application Chart — Compatible with Caterpillar Engines
| Category | Models |
|---|---|
| Truck Engine | 3126, 3126B, 3126E |
| Marine Engine | 3126B |
Before ordering: the 3126 family ran across many build years, power ratings and emissions specifications, and more than one module variant exists within it. The engine designation alone is not enough — compare the number stamped on your existing module’s data plate against 240-5303 or 10R-3571. If your label shows a different number, send us a photo of the plate along with your ESN and we will identify the correct part for you.
Technical Specifications
| Part Name | Electronic engine control module / engine control unit (ECM / ECU) |
| Reference Numbers | 240-5303, 2405303, 10R-3571, 10R3571 |
| Condition | Remanufactured, bench-tested before dispatch |
| Engine Family | 3126 series only — 3126, 3126B, 3126E |
| Installation Method | Direct replacement — no wiring or bracket modification |
| Programming | Required — must be flashed to your engine serial number |
| System Voltage | 12V / 24V DC — application dependent, confirm on data plate |
| Housing Material | Die-cast aluminium with sealed gasket interface |
| Connectors | Sealed multi-pin harness connectors, original pin layout |
| Rebuild Scope | Capacitors, injector driver components and solder joints renewed as measurement requires; conformal coating refreshed; seals replaced |
| Testing | 100% functional bench test under simulated load |
| Warranty | 6 months — repair or replacement service |
| Package Contents | 1 x engine control module (mounting hardware not included) |
This unit is an emissions-related component. It is supplied to restore factory-specified performance only, and is not modified, re-calibrated or altered in any way.
Common Failure Symptoms
These modules fail by ageing rather than by accident. After two decades of heat cycling and vibration the failure patterns are fairly predictable, and most of them look like something else first.
| Symptom | What It Usually Points To |
|---|---|
| Starts cold, fails to restart hot | The classic ageing-module pattern on this engine family. Cracked solder joints open as the board expands, then close again as it cools. If the truck restarts fine after an hour parked up, this is the first thing to suspect. |
| Engine cranks but will not start | No injector drive signal reaching the fuel system; verify power and ground at the module before condemning it. |
| Intermittent shutdown while driving | A failing internal supply that drops out under vibration and heat. On a module of this age, drifted electrolytic capacitors are the usual cause. |
| No communication with diagnostic software | Data link failure between the module and the service tool; check the connector and harness continuity first. On older trucks the data link wiring has often been disturbed by previous repairs. |
| Repeat injector driver fault codes | Output driver stage failure — codes return on multiple cylinders after new injectors are fitted. |
| Erratic or impossible sensor readings | Degraded internal reference voltage causing false pressure or temperature values across several channels at once. |
| Rough running, misfire or unstable idle | Inconsistent timing or fuelling control that persists after fuel system components have been ruled out. |
| Corrosion or moisture inside the connector | Failed housing seal allowing water ingress onto the board — common after twenty years of service, and a particular risk on 3126B marine installations. |
On a vehicle this old, check the wiring before the module. Battery condition, chassis and engine ground straps, charging voltage, chafed harness sections and corroded pins imitate module failure far more often than the module itself — and after two decades and several owners, most 3126 trucks have accumulated a few questionable repairs in the loom. A ground strap that has quietly corroded through will produce symptoms indistinguishable from a failing ECM. Confirm with a full diagnostic scan before replacing.
Shipping & Quality Guarantee
- 100% quality control — every module is functionally bench-tested and visually inspected before it leaves our facility.
- Dispatch in 1–3 business days via DHL, UPS or FedEx express, with tracking provided within 24–48 hours.
- Protective packaging — anti-static bag, foam-cushioned carton, sealed against moisture for international transit.
- 6-month warranty — if a fault arises within the period, we provide repair or replacement service.
- Technical support — send us your ESN, VIN and data plate photo and our team will confirm fitment before and after purchase.
Shipping & Customs Notice
The listed price covers the product, shipping and handling only. It does not include import duty, VAT, GST or any local taxes or customs clearance charges. Any such fees are levied by your national customs authority and remain the buyer’s responsibility. Please check your local import regulations before ordering.
All brand names, part numbers and model designations are used for identification and cross-reference purposes only. This product is manufactured and tested to aftermarket replacement standards and is not associated with, sponsored by or endorsed by any vehicle or engine manufacturer. All trademarks are the property of their respective owners.
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