Restore Peak Performance and Reliability to Your GM Truck
If you’re dealing with frustrating, hard-to-diagnose issues like stalling, poor fuel economy, erratic engine behavior, or a persistent check engine light, the problem often points directly to the heart of your vehicle’s electronics: the Powertrain Control Module (PCM). As a technician with over two decades of experience under the hood, I’ve seen firsthand how a failing engine computer can turn a reliable workhorse into a source of constant headaches. This isn’t just a part; it’s the solution to getting your truck back to factory-spec operation without the hassle and expense of a dealership visit.
This replacement PCM, part number 12586243, is the definitive fix for a wide range of 2004 GM vehicles. The most significant benefit we offer is our complimentary VIN-programming service. Before we ship your module, we flash it with the latest official GM software calibrated specifically to your vehicle. This means it arrives at your door ready for installation, eliminating the need for expensive scan tools or a trip to the dealer for programming. It’s the most direct path to resolving complex electronic issues and restoring the performance you depend on.
Case Study: A Tricky Diagnosis
I remember a 2004 Sierra 2500 with the 8.1L that came into the shop with a bizarre, intermittent no-start condition. The owner had already replaced the battery, alternator, and starter. It would run fine for days, then refuse to crank. When it did run, it had a rough idle. We scanned it and found a P0601 (Internal Control Module Memory Check Sum Error). While this code often points to the PCM, the intermittent nature made us check all the grounds and power feeds first—they were solid. After confirming the wiring harness was good, we knew the processor inside the original PCM was failing. A replacement, pre-programmed module like this one solved the problem instantly. The customer was back on the road the same day, saving hundreds compared to a dealership repair.
Is Your Vehicle Showing These Symptoms?
A failing PCM can manifest in numerous ways. If you’re experiencing any of the following, this module is the likely solution for your 2004 Silverado 3500 PCM issues:
- ✔ Unexplained Check Engine Light (CEL) illumination
- ✔ Stored diagnostic trouble codes (DTCs) such as P0601, P0602, P0606, or U0100
- ✔ Engine stalling, stumbling, or hesitating unexpectedly
- ✔ Harsh or erratic automatic transmission shifting
- ✔ A complete no-start or no-crank condition
- ✔ Noticeable decrease in fuel efficiency
- ✔ Failure to pass state emissions testing
A Straightforward Guide to Installation
Replacing the PCM on most of these GM trucks and vans is a job most DIYers can handle with basic tools. With our pre-programming, you skip the hardest part. Follow these general steps for a successful installation:
- Safety First: Always disconnect the negative terminal from your vehicle’s battery and wait at least 10 minutes for the system to fully discharge.
- Locate the Module: On your 2004 Silverado 3500, the PCM is located on the left-hand (driver’s) side, under the battery tray. For other models, refer to the fitment list for its location.
- Disconnect Connectors: Carefully release the locking tabs on the electrical wiring harnesses and pull them straight out from the module. Never force them. Inspect the pins for any corrosion or damage.
- Remove the Old PCM: Unbolt the mounting hardware that secures the old PCM to its bracket. Remove the old unit from the vehicle.
- Install the New PCM: Mount your new, pre-programmed module in place and secure it with the original hardware.
- Reconnect Everything: Firmly plug the wiring harnesses back into the new PCM until they click and lock into place. Reconnect the negative battery terminal.
- Perform Relearn Procedure: You may need to perform a security relearn procedure (often called a CASE relearn) for the vehicle to start. This procedure is simple and can typically be done without special tools. Instructions are widely available online or can be provided upon request.
Verified Vehicle Compatibility
This module is a direct replacement for part numbers 12586243 and 89017739. Please verify your part number and check the list below to ensure a perfect match for your vehicle. This is a crucial step for a successful repair.
- AVALANCHE 2500 04: Electronic Control Module; (LH front under battery)
- ASTRO 04: Electronic Control Module; (LH front by battery)
- BLAZER S10/JIMMY S15 04: Electronic Control Module; (RH front engine compartment)
- CORVETTE 04: Electronic Control Module; (RH engine compartment), ID 12586243
- CTS 04-05: Electronic Control Module; (RH engine compartment), V-Series, ID 12586243
- ENVOY XL/XUV 04: Electronic Control Module; 5.3L (next to air box), check ID
- EXPRESS/SAVANA VANS 1500/2500/3500 04: Electronic Control Module; (LH rear engine compartment)
- GTO 04: Electronic Control Module; main (LH engine)
- RAINIER 04: Electronic Control Module; 5.3L (next to air box), check ID
- S10/S15/SONOMA 04: Electronic Control Module; (RH front engine compartment)
- SAFARI (GMC) 04: Electronic Control Module; (LH front by battery)
- SIERRA/SILVERADO 1500 PICKUP 04: Electronic Control Module; (LH front under battery), 4.3L
- SIERRA/SILVERADO 2500/3500 PICKUP 04: Electronic Control Module; (LH front under battery), gasoline, 8.1L
- SSR 04: Electronic Control Module; (next to air box), check ID
- SUBURBAN 2500 04: Electronic Control Module; (LH front under battery), 8.1L
- TRAILBLAZER EXT 04: Electronic Control Module; 5.3L (next to air box), check ID
- YUKON XL 2500 04: Electronic Control Module; (LH front under battery), 8.1L
Frequently Asked Questions
Do I need to do anything after I install this 2004 Silverado 3500 PCM?
Because this module comes pre-programmed to your VIN, the main software is ready to go. However, you will likely need to perform a security relearn procedure, also known as a Crankshaft Variation (CASE) Relearn. This syncs the PCM with your vehicle’s anti-theft and crankshaft position sensor systems. It’s a simple key-on/key-off procedure that takes about 30 minutes and requires no special tools.
How do I provide my VIN?
After you complete your purchase, you will need to send us your vehicle’s 17-digit Vehicle Identification Number (VIN). You can typically add it as a note during checkout or send it to us in a message referencing your order number. We cannot program and ship the module without it.
Will this fix my transmission shifting problems?
In many cases, yes. The PCM controls both engine functions and transmission shift points. If the module itself is faulty, it can cause hard shifts, delayed shifting, or failure to shift. If the root cause of your issue is a failing PCM, this part will resolve it. However, it will not fix mechanical issues within the transmission itself.
Is this a used part?
This is a high-quality, inspected, and tested recycled OEM part. Each module is verified to be fully functional before being programmed with the latest GM software for your specific vehicle, ensuring reliable, long-term performance.