Is Your Late 90s GM Truck or Van Acting Up? It Could Be The PCM.
If you’re dealing with frustrating, hard-to-diagnose issues on your 1998-1999 GM vehicle, you’re not alone. These trucks and vans are legendary workhorses, but their electronic heart—the Powertrain Control Module (PCM)—can be a common point of failure after decades of service. A faulty PCM can cause a cascade of problems that might seem unrelated, from a simple check engine light to a vehicle that refuses to start. This isn’t just a part; it’s the central command for your engine and transmission, and when it fails, your vehicle’s reliability is gone.
This is a genuine, road-tested OEM Powertrain Control Module, a direct replacement for part number 9366810 and many others. We take the guesswork and hassle out of the repair by programming it specifically for your vehicle using your VIN. This means it arrives at your door with the latest GM software updates, ready for a straightforward installation. No expensive trips to the dealership for programming are required.
From the Diagnostic Bay
I remember a ’99 Silverado that came in on a tow truck. The owner was convinced his fuel pump had failed again—a common issue on these trucks. It would crank all day but never fire up. We checked fuel pressure, and it was perfect. We had spark. We were about to dive into the complex spider injection system when I decided to check communication with the PCM. My scan tool couldn’t connect. After verifying the PCM’s power and ground connections were solid, we knew we had a dead module. We swapped in a pre-programmed PCM just like this one, and the truck fired up on the first try. The customer saved hundreds, if not thousands, in diagnostic time and unnecessary parts.
Diagnosing a Faulty 1998-1999 GM Truck PCM
The PCM is responsible for managing everything from fuel mixture and ignition timing to transmission shift points. When internal components begin to fail, the symptoms can be erratic and confusing. Before condemning your module, always check the basics: battery voltage, grounds, and fuses. If those are good, look for signs that point directly to the computer.
Common Symptoms of a Failing GM PCM
- ✔ Check Engine Light: You may see codes related to internal module failure, memory errors, or processor faults (e.g., P0601, P0604, P0606).
- ✔ No-Start or Intermittent Starting: The engine cranks but won’t start because the PCM isn’t firing the injectors or ignition coils.
- ✔ Harsh or Erratic Shifting: The PCM controls the 4L60E or 4L80E transmission. A failing module can cause hard shifts, slipping, or failure to shift into certain gears.
- ✔ Poor Engine Performance: Unexplained stalling, rough idling, misfires, and a significant loss of power can all be traced back to a faulty PCM.
- ✔ No Communication: Your scan tool is unable to connect or communicate with the vehicle’s computer.
- ✔ Apparent Fuel or Spark Issues: The vehicle may act like it has a bad fuel pump or ignition module, but replacing those parts doesn’t solve the problem.
The Right Solution: A VIN-Programmed Replacement
Don’t settle for a generic, unprogrammed module from a salvage yard. Modern vehicles require precise software to function correctly. Our process ensures a seamless repair:
- Order the PCM: Complete your purchase for this part.
- Provide Your VIN: Reply to your order confirmation email with your vehicle’s 17-digit VIN.
- We Program It: Our technicians flash the module with the correct, updated GM software for your specific vehicle configuration.
- Install and Drive: The module arrives ready for installation. In most cases, it’s a plug-and-play process. Some vehicles may require a simple security relearn or CASE relearn procedure, which can be done without special tools.
By choosing our pre-programmed PCM, you are getting a cost-effective, reliable solution that restores your vehicle’s original performance and functionality. This module is compatible with a wide range of GM trucks, vans, and SUVs from 1998-1999, including the Savana, Express, Silverado, Sierra, Tahoe, Yukon, and more. Please verify your part number or use the fitment chart to confirm compatibility.
Frequently Asked Questions
Do I need to do anything after I install this PCM?
While we program the PCM to your VIN, some GM vehicles of this era may require a Crankshaft Variation Relearn (CASE Relearn) to prevent a P1336 trouble code. This procedure helps the PCM compensate for minor variations in the crankshaft position sensor and can often be performed by a qualified mechanic with a bidirectional scan tool or sometimes with a specific drive cycle.
How do I provide my VIN number?
After you place your order, simply reply to the confirmation email with your 17-digit Vehicle Identification Number (VIN). We cannot ship your part until we receive this information, as the programming is essential for the part to work.
Is this a new part?
No, this is a high-quality, tested, and guaranteed used OEM part sourced from a salvaged vehicle. We inspect each unit to ensure it is fully functional before programming and shipping.
Will this fix my transmission shifting problems?
If your transmission issues are caused by electronic commands from a faulty PCM, then yes, this part will likely solve the problem. The PCM directly controls the transmission solenoids. However, this will not fix internal mechanical failures within the transmission itself.
What if my part number isn’t an exact match to 9366810?
This PCM is a direct replacement for several service numbers, including 09355699, 16266645, 16250279, and others listed in the description. As long as your vehicle is listed in our compatibility chart, this module will work once programmed to your VIN.