Is Your Work Van Down? Get it Running Right.
If your 2004 Express 2500 is suddenly running rough, refusing to start, or has a persistent check engine light that won’t go away, a failing Powertrain Control Module (PCM) is a very likely culprit. As the brain of your vehicle’s engine and transmission, when the PCM starts to fail, it can cause a host of frustrating and confusing problems. I’ve spent years under the hoods of these vans, and I’ve seen it allโfrom intermittent no-starts that leave you stranded to poor fuel economy that costs you money on every job.
This isn’t just a replacement part; it’s a direct solution. We take a reliable, tested PCM and flash it with the latest official GM software updates specifically for your vehicle. All we need is your Vehicle Identification Number (VIN) during checkout. This ensures that when the module arrives, it’s ready to communicate perfectly with your van’s specific systems, restoring factory performance and reliability.
Why Choose a Pre-Programmed PCM?
- โ Eliminate Guesswork: Solves common issues like random misfires, harsh shifting, and no-communication codes.
- โ Save Time and Money: This module arrives ready to install. There is no need for an expensive trip to the dealership for programming, saving you hundreds of dollars and significant downtime.
- โ Latest Software: We flash your module with the newest GM-released calibrations, which can resolve factory bugs and improve engine efficiency and transmission performance.
- โ Guaranteed Compatibility: By programming to your VIN, we ensure this module is a perfect electronic match for your vehicle. This unit is a direct replacement for part numbers 89017739 and 12586243.
From the Shop Floor: A Real-World Diagnosis
“A customer’s 2004 Express 2500 work van came in last week with a persistent P0304 (Cylinder 4 Misfire). The owner had already replaced the plug, wire, and coil pack. The injector tested fine with our diagnostic tools. We hooked a lab scope to the injector signal wire right at the PCM connector and found our problem: the driver circuit inside the original PCM was completely dead. It wasn’t sending the signal to fire the injector. A new, programmed PCM fixed it instantly. It’s a common failure point I’ve seen on dozens of these hard-working vans.”
Easy Plug-and-Play Installation Guide
Installing your 2004 Express 2500 PCM is straightforward for a DIYer with basic tools. On the Express and Savana vans, the module is located in the rear of the engine compartment on the driver’s side.
- Safety First: Disconnect the negative terminal from your vehicle’s battery and wait 10-15 minutes for the system capacitors to discharge.
- Locate the PCM: Find the module on the driver’s side (LH) firewall/rear of the engine bay. It will have several large wiring harness connectors attached.
- Disconnect Harnesses: Carefully lift the locking tabs on each connector and pull them away from the module. Never force them; they are designed to release easily when the levers are actuated.
- Remove the Old Module: Unbolt the PCM from its mounting bracket. Keep the hardware, as you will reuse it.
- Install the New Module: Seat your new, pre-programmed PCM into the bracket and secure it with the original hardware.
- Reconnect Everything: Firmly plug the wiring harnesses back into the new module until they click and the locking tabs are secure. Reconnect your negative battery terminal.
- Final Step: Turn the key to the ‘ON’ position (without starting the engine) for 10-15 seconds before starting. This allows the other modules to recognize the new PCM. Your vehicle is now ready to drive.
Is This the Right Part for Your Vehicle?
This PCM is a guaranteed fit for a wide range of 2004 GM trucks, vans, and SUVs. While this listing focuses on the 2004 Express 2500 PCM, it is also the correct module for models like the Silverado, Sierra, Suburban, Yukon, Avalanche, Trailblazer, and more. Please use the fitment list provided to confirm your specific model and engine combination. Providing your VIN is the final, crucial step to ensure 100% correct programming and compatibility.