Restore Your Hummer’s Dominating Performance
Is your 2004 Hummer H2 suffering from poor performance, erratic shifting, or a persistent Check Engine Light? These are common signs that the brain of your vehicle, the Powertrain Control Module (PCM), is failing. This vital component manages everything from fuel injection and spark timing to transmission shifting and emissions control. When it falters, the entire vehicle’s performance and reliability are compromised. This replacement PCM, part number 12586242, is the definitive solution to get your H2 running strong again.
We take the guesswork and hassle out of the repair. Unlike a generic module from a parts store, this unit is professionally programmed specifically for your vehicle using your VIN. We install the latest, most stable software updates from GM, ensuring optimal performance, fuel efficiency, and longevity. This means no expensive trips to the dealership for programming—it arrives ready for installation.
From the Diagnostic Bay
We had a 2004 Sierra Denali come in with a frustrating intermittent no-start condition. The owner had already replaced the battery, alternator, and starter to no avail. Scans were inconclusive, showing only a few random communication codes. After checking the main power and grounds to the PCM, we noticed a slight discoloration on one of the connector pins. We swapped in a known-good, programmed PCM, and the truck fired up instantly and ran perfectly. It’s a classic case where the internal board of the original PCM was failing intermittently, causing a cascade of confusing symptoms that pointed away from the real culprit.
Common Symptoms of a Failing PCM
- ✔ Persistent Check Engine Light (CEL) on the dashboard.
- ✔ Vehicle fails to start or has difficulty starting (intermittent no-start).
- ✔ Rough idling, stalling, or poor engine performance.
- ✔ Decreased fuel economy for no apparent reason.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ Communication errors with diagnostic scan tools.
- ✔ Unexplained error codes for various sensors, even after replacement.
The Right 2004 Hummer H2 PCM for a Lasting Fix
This module is a direct replacement for OEM service number 12586242 and is also compatible with a wide range of other numbers, including YFKD, YFKF, YFKH, YFKJ, YFXL, and more. It’s not just for the Hummer H2; this versatile computer fits a variety of 2004 GM trucks and SUVs like the GMC Sierra, Chevy Silverado, Tahoe, Suburban, Escalade, and others equipped with the 5.3L or 6.0L engines. By providing your VIN upon purchase, you guarantee that the software loaded onto this module is precisely calibrated for your vehicle’s specific options and systems.
Installation is straightforward for a DIY mechanic or any professional technician. Located on the driver’s side front of the engine bay under the battery, the process involves disconnecting the battery, removing the old module, installing the new one, and reconnecting the battery. In many cases, a security relearn procedure may be necessary, which can be easily performed without special tools and typically takes about 30 minutes. Instructions for this procedure are readily available online.
Frequently Asked Questions
Do I need to do any programming after I receive this PCM?
No. This PCM comes fully programmed to your vehicle’s VIN with the latest GM software updates. It is ready for installation right out of the box. A security relearn procedure may be required, which does not involve any special tools.
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 placard on the driver’s side dashboard visible through the windshield.
Is this a plug-and-play part?
Yes, once we program it to your VIN, the module is designed to be a direct-fit, plug-and-play replacement. Simply disconnect the old unit and connect this one. As mentioned, a simple key-cycle security relearn might be needed.
How do I know if this PCM will fit my vehicle?
This module replaces service number 12586242 and many others listed in the description. It fits a wide range of 2004 GM trucks and SUVs. The most important step is to provide your VIN so we can ensure the programming is a perfect match for your vehicle’s configuration.
What if my original part number isn’t listed?
Please contact us with your vehicle’s VIN and the part number from your original computer. We can verify compatibility and ensure you receive the correct module for your specific application.