Is your 1998 GMC Envoy or compatible GM truck suffering from frustrating issues like a persistent check engine light, poor engine performance, stalling, or a no-start condition? These are classic signs of a failing Powertrain Control Module (PCM), the electronic brain of your vehicle. Don’t let a faulty computer keep you off the road. This fully programmed, tested, used PCM is the reliable and cost-effective solution to restore your vehicle’s performance and drivability.
From the Diagnostic Bay
We had a 1999 Chevy Tahoe come in that had its owner chasing ghosts for weeks. It would randomly stall at stoplights and had an intermittent check engine light for an oxygen sensor circuit that just wouldn’t clear, even after replacing the sensor. After checking all the wiring and finding no faults, we suspected the PCM. A quick swap with one of our programmed units, like this one, solved the problem instantly. The false O2 sensor code vanished, and the stalling stopped completely. It’s a reminder that a failing computer can send you down the wrong diagnostic path, making a direct-fit programmed module an invaluable repair tool.
Common Symptoms of a Failing 1998 Envoy PCM
- ✔ Persistent Check Engine Light (CEL) with various trouble codes.
- ✔ Engine stalling, stumbling, or hesitating during acceleration.
- ✔ No-start or hard-starting conditions, especially when warm.
- ✔ Noticeable decrease in fuel economy.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ Failure to pass emissions testing.
- ✔ Communication errors with diagnostic scan tools.
The Right Part, Programmed for Your Vehicle
This isn’t just a generic part off the shelf. We take the guesswork out of the repair by programming this module specifically for your vehicle using the 17-digit Vehicle Identification Number (VIN) you provide. This process ensures that the computer has the correct factory software and the latest updates from GM, matching all the specific options and calibrations your vehicle was built with. This VIN-specific programming is crucial for proper engine, transmission, and emissions system operation.
This module is a direct replacement for multiple service numbers, including 16258815, 09355699, 16266645, 9355699, 16250279, 09366810, and 9366810. It fits a wide range of GM trucks and vans from the late 90s, such as the Chevrolet Silverado, GMC Sierra, Tahoe, Yukon, Suburban, Express, Savana, and more. Please verify the part number or consult the detailed fitment list to ensure compatibility.
Installation and Setup
Replacing the 1998 Envoy PCM is a straightforward process. It is typically located in the engine bay. After disconnecting the battery and swapping the module, you may need to perform a simple security relearn procedure, often called a “Passlock Relearn” or “CASE Relearn.” This procedure syncs the new computer with your vehicle’s anti-theft system and crankshaft position sensor. This can usually be done without special tools and instructions can be readily found online for your specific model.
Frequently Asked Questions
Do I need to program this computer?
No. We handle all the programming for you before shipping. Simply provide your vehicle’s 17-digit VIN during or after checkout, and we will flash the module with the correct GM software for your exact vehicle.
Is this a new part?
This is a high-quality, tested used part sourced from a salvaged vehicle. Each unit is inspected and verified to be fully functional before being programmed and shipped.
What information do you need from me?
We require your complete 17-digit Vehicle Identification Number (VIN) to program the module correctly. You can usually find this on your driver’s side dashboard (visible through the windshield) or on your vehicle’s registration or insurance card.
Will I need to do anything after installing this PCM?
In many cases, you will need to perform a security relearn procedure to sync the module with your vehicle’s anti-theft system. This is a simple procedure that typically involves turning the key on and off in a specific sequence. A Crankshaft Variation Relearn (CASE Relearn) may also be necessary and requires a capable scan tool.
How can I be sure my PCM is the problem?
While the symptoms listed are very common for PCM failure, it’s always best to have a proper diagnosis performed. Check for solid power and ground connections at the module and rule out sensor or wiring issues first. If all other components check out, the PCM is the likely culprit.