Is Your Late-90s GM Truck or Van Running Rough?
If you’re dealing with frustrating issues like a persistent check engine light, sudden stalling, poor fuel economy, or erratic shifting in your 1998-1999 GM vehicle, the root cause might be a failing Powertrain Control Module (PCM). As the central computer for your engine and transmission, a faulty PCM can create a cascade of problems that are often misdiagnosed, leading to wasted time and money on unnecessary repairs. This module is the brain, and when it starts to fail, the entire vehicle’s performance suffers.
The Direct Solution for Your Vehicle’s Brain
This is a genuine, used GM Powertrain Control Module, service number 9355699, that has been fully tested and is ready for programming. We take the guesswork out of the repair. Before we ship this module to you, our technicians will program it with the latest GM-certified software using the specific Vehicle Identification Number (VIN) you provide. This ensures that the module is a perfect match for your vehicle’s engine, transmission, and factory options, restoring its original performance and reliability.
From the Diagnostic Bay
We had a 1999 Chevy Tahoe come into the shop with a problem that had stumped two other mechanics. The owner complained of a random misfire on cylinder 3, but only after the engine was fully warmed up. He had already replaced the spark plug, wire, distributor cap, rotor, and even the fuel injector. Nothing worked. After hooking up our diagnostic tools, we noticed the control signal for the #3 injector was dropping out intermittently. The problem wasn’t the injector itself, but the driver circuit inside the original PCM that was failing under heat. We installed one of our VIN-programmed modules, and the Tahoe ran perfectly. It’s a classic example of how a failing PCM can mimic other component failures.
Diagnosing a Failing 1998-1999 GM Truck PCM
The PCM in these GMT400 and related platform vehicles is a robust unit, but after decades of heat cycles and electrical stress, failure is common. A faulty computer can manifest in various ways, making diagnosis tricky. If you’ve checked the basics and are still having trouble, it’s time to consider the PCM as the culprit. This replacement 1998-1999 GM Truck PCM is the definitive fix for these electronic issues.
Common Symptoms of a Bad PCM:
- ✔️ Unexplained Check Engine Light (CEL) with various codes or no codes at all.
- ✔️ Engine stalling, stumbling, or misfiring, especially when warm.
- ✔️ Harsh, delayed, or erratic automatic transmission shifting.
- ✔️ Complete no-start condition where the engine cranks but will not fire.
- ✔️ Noticeable decrease in fuel economy.
- ✔️ Failure to pass state emissions testing.
- ✔️ Intermittent loss of communication with diagnostic scan tools.
VIN Programming is Essential
Unlike simple sensors, you cannot just swap a PCM from another vehicle and expect it to work. These modules are tied to the vehicle’s security system (Passlock) and contain specific data for the engine size, transmission type, and other options. Our service eliminates this complexity. By programming the module to your VIN, we ensure it’s a true plug-and-play solution. Once installed, you may need to perform a simple security relearn procedure, but no expensive dealer tools are required. We provide clear instructions for this process.
This module is a direct replacement for part numbers 09355699, 16266645, 16250279, 16258815, 09366810, and 9366810 and fits a wide range of Chevrolet, GMC, Cadillac, and Isuzu models from 1998 to 1999. Please verify your original part number or consult the detailed fitment list to confirm compatibility.
Frequently Asked Questions
What exactly is a PCM?
The Powertrain Control Module (PCM), often called an Engine Control Module (ECM), is your vehicle’s main computer. It controls critical functions like fuel mixture, ignition timing, and transmission shifting to ensure optimal performance, fuel efficiency, and low emissions.
Is this part difficult to install?
Physically, the installation is straightforward for a DIY mechanic. It typically involves disconnecting the battery, unplugging a few electrical connectors, and removing a few bolts. The module is usually located in the engine bay. We provide instructions for the simple security relearn procedure that may be required after installation.
Do I need to do any programming myself?
No. The main programming is done by us before the part is shipped. You just need to provide your vehicle’s VIN at checkout. This ensures the module is ready to be installed in your specific vehicle.
How do I find my original part number?
Your original part number is printed on a sticker on the PCM itself. You will need to locate the module in your vehicle (typically on the driver’s side fender or firewall) and read the large-print number, often labeled as the “Service No.”
What happens if I provide the wrong VIN?
Providing the correct VIN is critical. An incorrect VIN will result in a module that is not compatible with your vehicle’s systems, leading to a no-start condition or other major issues. Please double-check your VIN from your driver’s side door jamb or dashboard before submitting your order.
Is this a new part?
No, 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, offering a reliable and cost-effective solution.