Is your GM vehicle suffering from perplexing engine issues, a persistent check engine light, or a no-start condition? The Powertrain Control Module (PCM), often called the Engine Control Module (ECM), is the central computer responsible for your engine’s performance, efficiency, and emissions. A faulty module can lead to a cascade of problems that are often difficult to diagnose. This replacement PCM, part number 12586243, is the definitive solution for a wide range of 2004 and 2005 GM vehicles, including the high-performance Cadillac CTS-V, rugged Sierra/Silverado trucks, and versatile SUVs like the Envoy and Trailblazer.
We take the guesswork and hassle out of the replacement process. Unlike a generic module from a parts store or salvage yard, this unit comes fully programmed to your vehicle’s specific Vehicle Identification Number (VIN). We install the latest, most stable software updates from GM, ensuring optimal performance and compatibility. This means no expensive trips to the dealership for programming—it’s a true plug-and-play solution designed to get you back on the road quickly and confidently.
From the Diagnostic Bay
We had a 2005 Cadillac CTS-V come into the shop with a ghost of a problem. The owner complained of intermittent stalling at idle, but it would always start right back up. There were no consistent trouble codes, just a few random communication errors that would come and go. We checked everything—fuel pressure, ignition system, sensors, and wiring harnesses—and couldn’t find a fault. Finally, while monitoring live data on a long test drive, we saw the PCM’s data stream freeze just before it stalled. The module was overheating internally and failing intermittently. We replaced it with a VIN-programmed 2004-2005 CTS PCM like this one, and the phantom stalling vanished for good. It’s a classic example of how a failing computer can mimic a dozen other problems.
Common Symptoms of a Failing PCM
- ✔ Persistent and often inexplicable Check Engine Light (CEL)
- ✔ Engine stalling or shutting off while driving
- ✔ Rough idling or misfires
- ✔ A noticeable decrease in fuel economy
- ✔ Failure to pass emissions tests
- ✔ No-start or hard-starting conditions
- ✔ Harsh or erratic automatic transmission shifting
- ✔ Communication errors with diagnostic scan tools
Why Choose a VIN-Programmed Module?
Modern vehicles are complex systems. The PCM communicates with dozens of other modules, from the transmission controller to the anti-lock brake system. Simply installing a used or non-programmed module will result in a no-start condition due to anti-theft systems and mismatched component data. Our programming service ensures that the replacement PCM is a perfect digital match for your vehicle. We transfer all the critical data from your VIN, including engine and transmission calibrations, emissions settings, and security information. This makes the installation process as simple as swapping the physical part, saving you hundreds of dollars in dealership programming fees and towing costs.
Full Vehicle Fitment List
This module is a direct replacement for part numbers 12586243 and 89017739. Please verify your part number and check the comprehensive list below to ensure compatibility with your specific vehicle and options.
- Cadillac CTS (2004-2005): V-Series, (RH engine compartment)
- Chevrolet Corvette (2004): (RH engine compartment)
- Chevrolet SSR (2004): (Next to air box)
- Pontiac GTO (2004): (LH engine)
- Buick Rainier (2004): 5.3L (Next to air box)
- Chevrolet Avalanche 2500 (2004): (LH front under battery)
- Chevrolet & GMC Trucks (2004): Silverado/Sierra 1500 (4.3L), 2500/3500 (8.1L Gasoline)
- Chevrolet & GMC SUVs (2004): Suburban 2500 (8.1L), Yukon XL 2500 (8.1L), Trailblazer EXT (5.3L), Envoy XL/XUV (5.3L)
- Chevrolet & GMC Vans (2004): Express/Savana 1500, 2500, 3500
- Chevrolet & GMC S-Series (2004): S10, S15, Sonoma, Blazer, Jimmy
- Chevrolet & GMC Astro/Safari (2004): (LH front by battery)
Frequently Asked Questions
Do I need to get this PCM programmed by a dealer?
No. This module comes fully pre-programmed to your vehicle’s VIN. Simply provide us with your VIN at checkout, and we will flash the unit with the latest GM software before shipping. It will be ready to install right out of the box.
Where do I find my vehicle’s VIN?
Your 17-digit Vehicle Identification Number (VIN) can be found on your vehicle’s registration, insurance card, or on the driver’s side of the dashboard visible through the windshield. It may also be on a sticker in the driver’s side door jamb.
Will this fix my vehicle’s problem for sure?
This part will resolve your issue if the PCM is the root cause of the failure. While the symptoms listed are common for a bad PCM, they can also be caused by other faulty components. Proper vehicle diagnosis is always recommended before ordering.
Is any special procedure needed after installation?
In many cases, it is a simple plug-and-play installation. However, some GM vehicles may require a security relearn procedure or a Crankshaft Variation (CASE) relearn, which can often be done without special tools. Instructions for these procedures are widely available online for your specific model.
How can I be sure this is the right part for my car?
The best way is to match the part number from your original module. This unit replaces part numbers 12586243 and 89017739. You can also use the detailed fitment list provided on this page to confirm compatibility with your year, make, and model.