Is Your GM Truck or Van Running Rough?
If your 1998-1999 Chevrolet Express 3500, or another compatible GM vehicle, is experiencing baffling issues like stalling, erratic shifting, a persistent check engine light, or a complete no-start condition, the culprit is often a failing Powertrain Control Module (PCM). As the central computer of your vehicle, the PCM is responsible for managing everything from fuel injection and spark timing to transmission shift points and emissions controls. When it begins to fail, it can create a cascade of problems that are frustrating and difficult to diagnose.
Don’t let a faulty computer keep your reliable workhorse off the road. This is a genuine, used GM PCM, service number 9366810, that has been meticulously tested and is ready for installation. More importantly, we take the guesswork out of the replacement process. Before this module ships, we will program it specifically to your vehicle’s Vehicle Identification Number (VIN). This ensures that it has the correct factory calibration and the latest software updates from General Motors, making the installation process as smooth as possible.
From the Diagnostic Bay
We had a 1999 Chevy Suburban come in that had its owner chasing his tail for weeks. The complaint was a random, harsh 1-2 shift and an intermittent P0300 (Random Misfire) code. The owner had already replaced the spark plugs, wires, cap, and rotor. He even swapped the fuel pressure regulator. Nothing worked. After hooking up our scanner and monitoring live data, we noticed the fuel trim values were swinging wildly just before the harsh shift occurred. This pointed away from a purely mechanical or ignition issue and toward the computer’s logic. We swapped in a VIN-programmed PCM, performed the security relearn, and the truck drove perfectly. The original PCM’s internal processor was failing under load, causing it to miscalculate fuel and shift commands. It’s a classic case where the symptoms don’t immediately scream ‘computer failure’, but the PCM was the root cause all along.
Symptoms of a Failing Powertrain Control Module
- ✔ Persistent and unexplained Check Engine Light (CEL).
- ✔ Vehicle refuses to start or starts and immediately stalls.
- ✔ Poor engine performance, including misfires, hesitation, or rough idling.
- ✔ Decreased fuel economy for no apparent reason.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ Communication errors with diagnostic scan tools.
- ✔ Intermittent issues that seem to have no pattern and get worse over time.
The Importance of a VIN-Programmed 1998-1999 Express 3500 PCM
Simply installing a used PCM from another vehicle will not work. These late 90s GM vehicles use a sophisticated anti-theft system (Passlock/VATS) that links the PCM to your specific vehicle. Our VIN programming service correctly configures the module for your truck’s engine, transmission, and options. It also loads the most current GM software, which can resolve certain factory-known drivability issues. This pre-programming saves you a costly trip to the dealership and eliminates compatibility headaches. After installation, you will only need to perform a simple security relearn procedure, which can often be done without any special tools.
This module is a direct replacement for multiple part numbers, including 09355699, 16266645, 16250279, 16258815, and 09366810. Please verify the part number on your original module to ensure compatibility or check the extensive fitment list provided. Getting the right part, programmed correctly, is the key to a successful and lasting repair.
Frequently Asked Questions
How do I provide my VIN number?
After you complete your purchase, please send us a message with your 17-digit VIN. We cannot ship your order until we receive this information, as the programming is a critical part of the process.
Is this a plug-and-play part?
It is almost plug-and-play. Because we program it to your VIN, it will have the correct software for your engine and transmission. However, you will need to perform a security relearn procedure after installation to sync the new PCM with your vehicle’s anti-theft system. This procedure typically takes 10-30 minutes and instructions can be easily found online for your specific model.
What if my original part number is different?
This PCM, service number 9366810, is a compatible replacement for several other part numbers like 09355699 and 16266645. As long as your vehicle is on the compatibility list and your original module is one of the listed part numbers, this unit will function correctly once programmed.
Is this a new or used 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. This provides a reliable and cost-effective solution compared to sourcing a new module.
Do I need to do a CASE relearn?
A Crankshaft Variation Relearn (CASE relearn) may be required to prevent a P1336 trouble code. This procedure requires a bi-directional scan tool. Many vehicles will run perfectly fine without it, but for optimal performance and to ensure the misfire detection system is calibrated, we recommend having it performed by a qualified mechanic if the code appears.