Restore Your Truck’s Performance and Reliability
Is your 2004 GMC Sierra 1500 giving you headaches with erratic behavior, a persistent Check Engine Light, or a frustrating no-start condition? You’re not alone. The Powertrain Control Module (PCM), the electronic brain of your truck, is a common point of failure that can cause a host of confusing issues. This replacement PCM, part number 12586243, is the definitive solution to get your dependable truck back on the road, running just as it should. We take the guesswork and high dealership costs out of the equation by pre-programming this module specifically for your vehicle using your VIN.
A Technician’s Notebook
I remember a 2004 Silverado that came into the shop with a laundry list of problems: harsh shifting, stalling at idle, and a check engine light with a code for a faulty throttle position sensor. The owner had already replaced the sensor twice with no luck. After connecting my scan tool, I noticed intermittent communication loss with the PCM. This is a classic red flag. Instead of just chasing codes, we checked the PCM’s power and ground circuits, which were solid. The real culprit was an internal failure in the original PCM, causing it to send faulty data and misinterpret sensor readings. Installing a properly programmed 2004 Sierra 1500 PCM like this one solved every single issue instantly. It’s a powerful reminder that the module itself can be the source of many seemingly unrelated problems.
Is Your Sierra Showing These Red Flags?
A failing PCM can manifest in various ways. If you’re experiencing any of the following, it’s a strong indicator that your engine’s computer needs attention:
- ✔ Check Engine Light is on with codes like P0601, P0606 (Internal Control Module Failure) or U-series communication codes.
- ✔ The engine cranks but refuses to start.
- ✔ Unexplained drops in fuel economy.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ The vehicle stalls intermittently, either while driving or at idle.
- ✔ Apparent failure of multiple sensors at once.
Straightforward Swap: Your PCM Installation Guide
Replacing the 2004 Sierra 1500 PCM is a job most DIYers can handle with basic tools. Our pre-programming service eliminates the need for a trip to the dealer for software flashing.
- Safety First: Always disconnect the negative terminal from your truck’s battery before starting any electrical work.
- Locate the PCM: On most 2004 Sierra/Silverado models, the PCM is located on the driver’s side of the engine bay, under the battery tray. You may need to remove the battery and its tray to gain access.
- Disconnect the Connectors: Carefully unlatch and remove the electrical wiring harness connectors from the old PCM. Inspect the connectors for any corrosion or damage.
- Remove the Old Module: Unbolt the old PCM from its mounting bracket and remove it from the vehicle.
- Install the New PCM: Mount your new, pre-programmed PCM onto the bracket and securely tighten the bolts.
- Reconnect Everything: Plug the wiring harness connectors firmly into the new module. Reinstall the battery tray and battery, then reconnect the negative battery terminal.
- Perform Security Relearn: You will need to perform a simple security relearn procedure (often called a CASE relearn) to sync the new PCM with your truck’s anti-theft system. This typically involves turning the key to the ‘ON’ position for 10-15 minutes, then off, and repeating two more times before starting the engine.
Verified Fitment for Your GM Vehicle
This module is a direct replacement for part numbers 12586243 and 89017739. It fits a wide range of 2004 GM vehicles, but always confirm your specific application by matching the part number or contacting us with your VIN. Key compatible models include:
- ✔ 2004 GMC Sierra 1500/2500/3500
- ✔ 2004 Chevrolet Silverado 1500/2500/3500
- ✔ 2004 Chevrolet Avalanche 2500
- ✔ 2004 GMC Yukon XL 2500
- ✔ 2004 Chevrolet Suburban 2500
- ✔ 2004 Chevrolet Express & GMC Savana Vans (1500/2500/3500)
- ✔ 2004 GMC Envoy, Chevrolet Trailblazer, & Buick Rainier (5.3L)
- ✔ 2004 Chevrolet SSR
- ✔ 2004 Pontiac GTO
- ✔ 2004 Chevrolet Corvette
- ✔ 2004-2005 Cadillac CTS-V
- …and many more. Please check the detailed fitment list or contact us to verify.
Do I need to do any programming myself?
Do I need to do any programming myself?
No. We handle the programming for you before shipment. Simply provide us with your vehicle’s VIN (Vehicle Identification Number) during or after checkout, and we will flash the module with the latest GM-certified software for your specific truck. This makes the installation process much simpler.
What is a CASE Relearn and is it difficult?
A CASE (Crankshaft Angle Sensor Error) Relearn is a procedure that syncs the new PCM with your engine’s crankshaft position sensor. While our programming handles the core functions, this final sync must be done in the vehicle. It often requires a capable bi-directional scan tool. Many local repair shops can perform this for a small fee if you don’t have the tool.
Is this a direct replacement for my 2004 Sierra 1500 PCM?
Yes, this module, part number 12586243, is a direct-fit replacement for the original electronic control module on a 2004 GMC Sierra 1500 with the 4.3L V6 engine (without hybrid option). It also fits a wide variety of other GM vehicles from that year. Always match your original part number to ensure compatibility.
Where do I find my VIN?
Your 17-digit VIN can be found on a metal plate on the driver’s side of the dashboard (visible through the windshield), on the driver’s side door jamb sticker, or on your vehicle’s registration and insurance documents.
Will this fix my transmission shifting problems?
In many cases, yes. The PCM controls both engine and transmission functions. If the module is failing, it can cause poor communication with the transmission control module (TCM) or send incorrect signals, leading to harsh or delayed shifts. Replacing a faulty PCM often resolves these types of electronic transmission issues.