Is Your 2004 Express 3500 Running Rough? The ECM Might Be the Culprit.
The Engine Control Module (ECM), often called the Powertrain Control Module (PCM), is the central computer of your vehicle’s engine. It controls everything from fuel injection and ignition timing to transmission shift points and emissions systems. When this critical component begins to fail, it can cause a wide array of confusing and frustrating problems, leaving your reliable workhorse van or truck feeling unpredictable. If you’re dealing with a persistent check engine light, poor performance, or stalling issues, a failing ECM is a likely cause.
This replacement Engine Control Module is a direct-fit solution, pre-programmed specifically for your vehicle. We take the guesswork out of the repair by flashing the module with the latest official GM software updates using your vehicle’s unique Vehicle Identification Number (VIN). This ensures that once you receive the part, it’s ready for a straightforward installation, restoring your vehicle’s original performance, reliability, and efficiency.
From the Diagnostic Bay
We had a 2004 Savana 2500 (which uses the same ECM) come into the shop with a bizarre complaint. The owner, a plumber, said it would randomly stall at stoplights, but only after it had been running for over an hour. No check engine light, no stored codes. We checked fuel pressure, ignition components, and sensors—everything looked perfect. On a hunch, we monitored the live data stream from the ECM on a long test drive. Sure enough, after about 75 minutes, we saw the injector pulse width data start to fluctuate wildly just before it stalled. The ECM was getting heat-soaked and failing internally. We installed a VIN-programmed module just like this one, and the van has been running flawlessly for him ever since. Sometimes, the problem lies deep within the vehicle’s brain.
Common Symptoms of a Failing 2004 Express 3500 ECM
- ✔ Check Engine Light: The most common indicator, often with codes related to sensors, communication, or processor faults.
- ✔ Engine Stalling or Misfiring: The engine may stall unexpectedly, run rough, or misfire as the ECM struggles to manage fuel and spark.
- ✔ Poor Fuel Economy: Incorrect fuel mixture calculations can lead to a noticeable drop in MPG.
- ✔ No-Start Condition: The vehicle may crank but refuse to start if the ECM isn’t activating the fuel pump or ignition system.
- ✔ Harsh or Erratic Shifting: The ECM works with the transmission controller, and a fault can lead to poor automatic transmission performance.
- ✔ Loss of Power: Your vehicle may feel sluggish or unresponsive due to incorrect engine parameters.
- ✔ Intermittent Issues: Problems may appear and disappear, often getting worse as the engine warms up.
A Plug-and-Play Solution
Don’t let a complex computer issue keep your vehicle off the road. Our process is designed to be simple and effective. After placing your order, you simply provide us with your vehicle’s VIN. Our technicians will then program this module to match your vehicle’s exact specifications. This means no expensive trips to the dealership for programming. The module arrives at your door ready to be installed. In many cases, after installation, a simple security relearn procedure is all that’s needed to get you back on the road.
This module is a reliable replacement for original equipment part numbers 89017739 and 12586243 and fits a wide range of 2004 GM vehicles, including the Chevrolet Express, GMC Savana, Silverado, Sierra, Trailblazer, Corvette, and many more. Please verify the part number and check the extensive fitment list to ensure compatibility with your specific model and engine.
Frequently Asked Questions
Do I need to have this ECM programmed?
No, this module comes pre-programmed to your vehicle’s VIN. After you place your order, you will need to provide us with your VIN so we can flash the unit with the correct software before shipping.
Is this a difficult part to install?
The physical installation is typically straightforward. It involves disconnecting the battery, unplugging the electrical connectors, and unbolting the old module. However, some vehicles may require a security relearn procedure (often called a CASE relearn or anti-theft relearn) after installation, which can usually be done without special tools. Instructions are widely available online for this process.
Where do I find my VIN?
Your 17-digit Vehicle Identification Number (VIN) can be found on your vehicle’s registration, insurance card, or on a plate on the driver’s side dashboard visible through the windshield.
Will this fix my check engine light?
If the check engine light and other symptoms are caused by a faulty ECM, then this part will resolve the issue. It’s always recommended to have your vehicle properly diagnosed to confirm the ECM is the point of failure before ordering.
Is this compatible with other GM vehicles?
Yes, this ECM fits a very wide range of 2004 GM trucks, vans, and SUVs. Please review the detailed compatibility list on this page to confirm it fits your specific make, model, and engine combination.