Restore Your Vehicle’s Brain and Get Back on the Road
Is your 1998 GMC Envoy, Chevy truck, or GM van suddenly running rough, stalling, or refusing to start? Are you staring at a persistent Check Engine Light and dealing with frustrating performance issues? Before you spend a fortune at the dealership, consider the heart of your vehicle’s operating system: the Powertrain Control Module (PCM). This isn’t just a part; it’s the central command for your engine and transmission. When it fails, it can cause a cascade of problems that are often misdiagnosed.
We offer a dependable, tested, and ready-to-install solution. This is a genuine OEM PCM, part number 16266645, carefully sourced from a salvaged vehicle. The real value, however, is in our service. We flash the module with the latest GM software updates and program it specifically to your vehicle’s VIN before it ships. This eliminates the need for expensive programming tools or a trip to the dealer, making it a straightforward fix for both seasoned mechanics and determined DIYers. Getting your truck or SUV running right again has never been simpler.
A Technician’s Notebook: The Intermittent Stall Mystery
I remember a 1998 Chevy Blazer that came into the shop with a problem that was driving the owner crazy. It would run perfectly for days, then suddenly stall at a stoplight and refuse to restart for 10-15 minutes. No consistent codes were stored, just a random misfire code every now and then. We checked fuel pressure, ignition components, and sensor data—everything looked fine. After days of chasing ghosts, we put a scope on the PCM’s power and ground circuits. We noticed that after about 20 minutes of runtime, as the engine bay heated up, the 5-volt reference signal from the PCM would start to fluctuate wildly. The internal voltage regulator was failing under heat. We swapped in a programmed PCM like this one, and the Blazer ran flawlessly. It’s a classic example of how a failing 1998 Envoy PCM can create symptoms that seem unrelated to the computer itself.
Is Your GM Vehicle Showing These Symptoms?
A failing PCM can manifest in many ways. If you’re experiencing any of the following, this module is a very likely solution:
- ✔ Unexplained Check Engine Light with codes like P0601 (Internal Control Module Memory Check Sum Error) or P0606 (PCM Processor Fault).
- ✔ Vehicle will not start or is very hard to start.
- ✔ Rough idling, stalling, or stumbling during acceleration.
- ✔ Noticeable decrease in fuel economy.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ Communication errors with diagnostic scan tools.
A Straightforward Guide to Installation
Replacing the PCM in these GM vehicles is a job most DIYers can handle in under an hour. While specific locations vary slightly, the process is generally the same.
- Safety First: Disconnect the negative terminal from your vehicle’s battery and secure it away from the post to prevent accidental contact.
- Locate the PCM: On the 1998 GMC Envoy, Blazer, and Jimmy, it’s typically located in the engine compartment on the right-hand (passenger) side. On full-size trucks and vans, it’s often on the left-hand (driver) side inner fender.
- Disconnect the Connectors: Carefully unclip and remove all wiring harness connectors from the old PCM. These connectors are color-coded to prevent mix-ups.
- Remove the Old Module: Unbolt the old PCM from its mounting bracket. Keep the hardware as you’ll reuse it.
- Install the New Module: Mount your new, pre-programmed PCM onto the bracket and securely fasten it.
- Reconnect Everything: Plug the wiring harnesses back into the corresponding sockets on the new PCM. Reconnect your battery terminal.
- Perform Security Relearn (If Needed): In most cases, this module is plug-and-play. However, some vehicles may require a simple security relearn procedure (often called the “Passlock Relearn”). This can be done without special tools and typically involves turning the key to the ‘ON’ position for 10-15 minutes. Instructions are widely available online for your specific model.
Verified Vehicle Compatibility
This module, identified by service number 09355699, is a direct replacement for part number 16266645 and other interchangeable numbers. It is compatible with a wide range of GM trucks, vans, and SUVs. Please match your part number or vehicle from the list below to ensure a perfect fit.
Compatible Part Numbers: 09355699, 16266645, 16250279, 16258815, 09366810, 9366810
Fits Models Including:
- 1998-1999 Chevrolet & GMC C/K 1500, 2500, 3500 Pickups (Gasoline)
- 1998-1999 Chevrolet Suburban & Tahoe (Gasoline)
- 1998-1999 GMC Yukon
- 1999 Cadillac Escalade
- 1998-1999 Chevrolet Express & GMC Savana 1500, 2500, 3500 Vans (Gasoline)
- 1998 Chevrolet Astro & GMC Safari
- 1998 Chevrolet S10, GMC Sonoma, Isuzu Hombre (4.3L V6)
- 1998 Chevrolet Blazer & GMC Jimmy (4.3L V6)
- 1998 Oldsmobile Bravada (4.3L V6)
- 1998 GMC Envoy (4.3L V6)
Note: For some 1998 S-10/Blazer platform vehicles, please verify you do not have build date option ZN4 (extended build date). This part fits standard 1998 models.
How does the VIN programming work?
How does the VIN programming work?
After you complete your purchase, you will need to provide us with your vehicle’s 17-digit VIN. Our technicians use this number to access the latest official GM software for your specific vehicle and flash it onto the module before shipping. This ensures perfect compatibility with your engine, transmission, and options.
Is a used PCM reliable?
Absolutely. We source these from tested, operational vehicles. Unlike many aftermarket parts, this is a genuine OEM component built to GM’s original quality standards. By flashing it with new software, we are also able to correct potential factory bugs, making it a very reliable and cost-effective repair.
Do I need to do anything else after installation?
In many cases, it’s a simple plug-and-play installation. However, on vehicles equipped with the Passlock anti-theft system, you may need to perform a quick security relearn procedure. This process syncs the new PCM to your vehicle’s security system and can be done at home without any special tools.
How do I find my original part number?
Your original part number is printed on a sticker on the PCM itself. You will need to locate the module on your vehicle to find it. However, as long as your vehicle is on our compatibility list, this module will work, as we program it to your VIN.