Is Your GM Truck or Van Running Rough?
The Powertrain Control Module, or PCM, is the central computer of your 1998-1999 GM vehicle. It manages everything from fuel injection and spark timing to transmission shifting and emissions controls. When this critical component begins to fail, it can cause a wide range of frustrating and difficult-to-diagnose problems. Your once-reliable Chevrolet Express, GMC Savana, Tahoe, or Suburban might start stalling, running rough, shifting erratically, or failing to start altogether. Don’t let a faulty computer keep your vehicle off the road.
From the Diagnostic Bay
We recently had a 1999 GMC Yukon in the shop with a persistent P0300 (Random Misfire) code that just wouldn’t clear. The owner had already replaced the spark plugs, wires, distributor cap, and rotor to no avail. After hooking up our diagnostic scanner, we noticed the fuel trim data was erratic and inconsistent. A deeper dive into the PCM’s live data revealed that the injector driver for cylinder 3 was intermittently failing. Instead of chasing more mechanical parts, we installed a VIN-programmed PCM like this one. The misfire vanished, the fuel trims stabilized, and the Yukon ran smoothly for the first time in months. It’s a classic case where the root cause was electronic, not mechanical.
Symptoms of a Failing 1998-1999 Express 1500 PCM
A failing PCM can manifest in numerous ways, often mimicking other component failures. If you’re experiencing any of the following issues, your engine computer could be the culprit. This replacement module is the definitive solution to restore your vehicle’s performance and reliability.
- ✔ Check Engine Light: An illuminated Check Engine Light with codes pointing to internal module failure, sensor circuits, or communication errors.
- ✔ No-Start or Hard-Start: The engine cranks but refuses to start, or takes an excessively long time to fire up.
- ✔ Stalling and Rough Idle: Your vehicle may stall unexpectedly at stops or idle erratically, surging or dipping in RPMs.
- ✔ Poor Fuel Economy: A faulty PCM can’t efficiently manage the engine, leading to a noticeable drop in gas mileage.
- ✔ Failed Emissions Test: Incorrect air/fuel mixture or sensor readings will almost certainly cause a failed smog check.
- ✔ Erratic Transmission Shifting: Since the PCM also controls the transmission, you might experience harsh shifts, delayed engagement, or getting stuck in a single gear.
Plug-and-Play Solution, Programmed for You
This is not a generic, one-size-fits-all part. This is a genuine, used OEM PCM sourced from a salvaged vehicle, ensuring perfect compatibility and function. The key to our service is that we program the module to your vehicle’s specific 17-digit VIN before it ships. This process loads the latest GM-approved software and vehicle-specific calibrations, making installation as simple as possible. Once you receive the part, you’ll simply need to perform a straightforward security relearn procedure, which can be done without any special tools. This ensures your vehicle’s anti-theft system recognizes the new computer and allows the engine to start.
This module is a direct replacement for multiple part numbers, including 09355699, 16266645, 9355699, 16250279, 16258815, 09366810, and 9366810. Please verify the part number on your original module or consult the extensive fitment list to confirm compatibility.
Frequently Asked Questions
Do I need to get this PCM programmed?
No. We handle the programming for you before we ship the part. All you need to do is provide us with your vehicle’s 17-digit VIN during or after checkout. This ensures the module has the correct software for your specific engine, transmission, and options.
What is a security relearn procedure?
After installation, your vehicle’s anti-theft system (PassLock/VATS) needs to synchronize with the replacement PCM. This is a simple procedure that typically involves turning the key to the ‘ON’ position for 10-15 minutes, then off, and repeating two more times. Instructions are readily available online for your specific model and it requires no special tools.
Is this a new computer?
No, this is a high-quality, tested, and fully functional used OEM computer recovered from a salvaged vehicle. This provides OEM-level reliability at a fraction of the cost of a new dealership part.
Will this fix my transmission shifting problems?
It certainly can. In these 1998-1999 GM vehicles, the PCM controls both the engine and the transmission. If your shifting issues are caused by faulty electronic commands from the computer, this replacement module is the correct fix.
How 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 metal plate on the driver’s side of the dashboard, visible through the windshield.