Is your 2004 GM truck or SUV running rough, stalling, or showing a persistent check engine light? These are classic signs of a failing Powertrain Control Module (PCM), the central computer that manages your engine’s performance. This replacement PCM, part number 12586242, is the definitive solution to restore your vehicle’s reliability and drivability. It arrives at your door fully programmed to your vehicle’s specific Vehicle Identification Number (VIN), ensuring a seamless, plug-and-play installation.
From the Diagnostic Bay
I remember a 2004 Sierra 1500 that came in with the most frustrating problem. The owner said it would randomly stall at stoplights, but never consistently. We checked fuel pressure, sensors, wiring—everything looked fine. No hard codes were stored, just some weird communication glitches. On a hunch, we monitored the PCM’s live data and noticed the processor would occasionally drop out. We swapped in a VIN-programmed module just like this one, and the problem vanished instantly. It’s a reminder that when the vehicle’s “brain” gets tired, the symptoms can be unpredictable and maddening.
Common Symptoms of a Failing 2004 GM PCM
If you’re experiencing any of the following issues, a faulty engine computer is a likely culprit. This module is designed to correct these problems and get you back on the road with confidence.
- ✔ Persistent Check Engine Light (CEL) that won’t clear
- ✔ Rough or erratic engine idling
- ✔ Unexplained stalling or cutting out while driving
- ✔ Noticeable decrease in fuel economy
- ✔ Harsh or incorrect automatic transmission shifting
- ✔ Engine misfires or hesitation during acceleration
- ✔ Complete no-start condition where the engine cranks but won’t fire
- ✔ Communication errors with diagnostic scan tools
The Importance of VIN Programming
Unlike a generic, off-the-shelf part, this PCM is not a one-size-fits-all solution. Modern GM vehicles have complex systems that require the PCM to be precisely calibrated to the specific options and components installed from the factory. By providing your VIN during checkout, our technicians will flash the module with the latest, most stable GM software updates for your exact vehicle. This critical step ensures all engine and transmission parameters are correct, prevents compatibility issues, and often improves performance and efficiency over the original software.
This module is a direct replacement for service part number 12586242 and is also compatible with the following service numbers: 19299226, 89017738, YFKD, YFKF, YFKH, YFKJ, YFKX, YFXL, YFXM, YFXN, YFXP, and YHTN. Please verify your original part number to ensure compatibility.
Installation and Setup
Installation is straightforward for a DIY mechanic with basic tools. On most compatible models like the Envoy, Trailblazer, and Rainier, the PCM is located in the engine bay next to the airbox. On trucks like the Silverado and Sierra, it’s typically found on the driver’s side, under the battery tray. Always disconnect the negative battery terminal before beginning the replacement. Once the new module is installed and the battery is reconnected, you may need to perform a security relearn procedure, which can often be done without special tools. Instructions are widely available online for your specific model.
Frequently Asked Questions
Do I need to get this PCM programmed?
No. We handle all the programming for you before shipment. Simply provide your vehicle’s VIN when you place your order, and the module will arrive ready to install with the latest GM software for your specific vehicle.
Where is the PCM located on my 2004 GM vehicle?
The location varies slightly by model. On mid-size SUVs like the Envoy, Trailblazer, and Rainier, it’s usually in the engine bay near the air filter box. On full-size trucks and SUVs like the Silverado, Sierra, Tahoe, and Yukon, it is typically mounted on the driver’s side frame rail area, beneath the battery.
What information do you need from me to program the module?
All we need is your 17-digit Vehicle Identification Number (VIN). You can find this on your vehicle’s registration, insurance card, or on the driver’s side of the dashboard visible through the windshield.
Will this fix my check engine light?
If the check engine light is caused by a faulty PCM, then yes, this part will resolve the issue. However, it’s always recommended to have the codes read by a professional or with a scan tool to confirm the PCM is the root cause before ordering.
Is any additional setup required after installation?
In many cases, the vehicle will start and run immediately. Some GM vehicles may require a security relearn procedure (also known as a CASE relearn or Passlock relearn) to sync the new PCM with the vehicle’s anti-theft system. This procedure can typically be done without special tools and takes about 30 minutes.