Is Your GM Truck or Van Running Rough?
If your 1998-1999 Chevrolet Express, GMC Savana, or other compatible GM vehicle is suffering from mysterious engine problems, a failing Powertrain Control Module (PCM) is a likely culprit. As the central computer for your engine, the PCM controls everything from fuel mixture and ignition timing to transmission shifting and emissions. When it starts to fail, it can cause a cascade of frustrating and difficult-to-diagnose issues, leaving you stranded or dealing with poor performance and fuel economy.
The Brain of Your Engine
Think of the PCM as the mission control for your vehicle’s powertrain. It constantly analyzes data from dozens of sensors throughout the engine and transmission to make real-time adjustments. A faulty module can send incorrect signals, leading to symptoms that might seem unrelated. Replacing a bad PCM isn’t just about swapping parts; it’s about restoring the core logic that makes your vehicle run correctly and efficiently.
From the Diagnostic Bay
We had a 1998 GMC Savana 2500 work van come into the shop that was a real head-scratcher. The owner said it would randomly stall at idle and sometimes wouldn’t start at all, but there were no consistent trouble codes. We checked fuel pressure, spark, and all the usual suspects, but everything looked fine. The scan tool would intermittently lose communication with the engine computer. That was the key. After verifying the wiring and connectors were solid, we pinpointed a failing internal processor in the original PCM. We installed one of our VIN-programmed modules, performed the quick security relearn, and the van fired up instantly and ran perfectly. The customer was back on the road making money the same day, without a costly trip to the dealership.
Common Symptoms of a Failing PCM
- ✔ Persistent Check Engine Light (CEL) that won’t clear or returns immediately.
- ✔ Engine stalling, stumbling, or hesitating during acceleration.
- ✔ Rough or erratic idling.
- ✔ A noticeable drop in fuel efficiency.
- ✔ Harsh or incorrect automatic transmission shifting.
- ✔ Complete no-start or no-spark condition.
- ✔ Scan tool cannot communicate with the engine computer.
- ✔ Unexplained error codes for various sensors.
Your Direct-Fit Solution: The 1998-1999 Express 1500 PCM
This is a genuine, used OEM Powertrain Control Module, part number 09366810, that has been carefully inspected and is ready for service. The biggest challenge with replacing a PCM is the vehicle-specific programming it requires. We solve that problem for you. Before we ship your module, our technicians will flash it with the latest GM-certified software updates and program it specifically to your vehicle’s Vehicle Identification Number (VIN). This critical step ensures that the computer works seamlessly with your engine, transmission, and all related systems, just as it did from the factory.
By providing your VIN upon purchase, you receive a module that is ready for installation right out of the box. This eliminates the need for expensive programming tools or a trip to the dealership, saving you significant time and money. The process is simple: install the module, perform a quick security relearn procedure (if required), and get your truck or van running reliably again.
Guaranteed Compatibility
This module is a direct replacement for a wide range of 1998-1999 GM trucks and vans. It is compatible with multiple service numbers, including 09355699, 16266645, 9355699, 16250279, 16258815, and 09366810. Please verify the part number on your original module and consult our detailed fitment list to ensure this is the correct part for your specific vehicle and engine configuration.
Frequently Asked Questions
What’s the difference between a PCM, ECM, and ECU?
These terms are often used interchangeably. ECM (Engine Control Module) and ECU (Engine Control Unit) typically refer to a computer that only manages engine functions. A PCM (Powertrain Control Module) is more integrated and controls both the engine and the automatic transmission. For this generation of GM vehicles, it is correctly called a PCM.
Do I need to do anything after installing this module?
Because we program the module to your VIN, it is nearly a plug-and-play installation. However, on many GM vehicles of this era, you will need to perform a simple security relearn procedure, also known as the Passlock or VATS relearn. This can typically be done without special tools and involves a sequence of key turns. Instructions are widely available online for your specific model.
How do I provide my VIN?
After you complete your purchase, you can send us a message with your 17-digit VIN. We cannot ship the module until we receive this information, as the programming is essential for the part to function in your vehicle.
Is this a new part?
No, this is a high-quality, used OEM part sourced from a salvaged vehicle. Each unit is thoroughly inspected and tested to ensure it is fully functional before being programmed and shipped. This provides OEM reliability at a fraction of the cost of a new module.
What happens if I install this without programming?
An unprogrammed PCM will not work correctly. At best, the vehicle may not start due to security mismatches (anti-theft). At worst, it could have incorrect fuel and timing parameters that could damage your engine. Our VIN programming service is essential for a successful repair.