Is Your 1998-1999 GM Truck Running Rough? The PCM Might Be the Culprit.
The Powertrain Control Module, or PCM, is the electronic brain of your 1998-1999 GMC 3500 Pickup. It’s a sophisticated computer that controls everything from fuel injection and ignition timing to transmission shifting and emissions systems. When this critical component begins to fail, it can cause a cascade of confusing and frustrating problems, often leaving you stranded or dealing with poor performance. A failing PCM can mimic other issues, making diagnosis a challenge. If you’re experiencing erratic engine behavior, poor fuel economy, or a persistent check engine light, it’s time to consider the heart of your vehicle’s management system.
This is a direct replacement PCM, service number 09355699, sourced from a salvaged vehicle and meticulously tested for full functionality. We take the guesswork out of the repair by programming the module specifically for your truck using your Vehicle Identification Number (VIN). This ensures that all factory settings, security information (Passlock/VATS), and operational parameters are a perfect match for your vehicle’s original configuration. By installing the latest GM software updates, we also ensure your engine and transmission operate with the most current logic for optimal efficiency and performance.
From the Diagnostic Bay
We had a ’99 Chevy Suburban come into the shop on a tow truck. The customer said it would crank but never start, and when it did, it would die immediately. He had already replaced the fuel pump, crank sensor, and ignition coil, but nothing worked. The check engine light was on, but his cheap scanner couldn’t communicate with the computer. That was our first clue. We hooked up our professional scan tool and also found no communication. After verifying the PCM had proper power and ground at the connectors, we knew the module itself was dead. We sourced a quality used unit, programmed it to the Suburban’s VIN, performed the quick security relearn, and it fired up on the first try. It’s a classic failure mode for these late 90s GM PCMs.
Common Symptoms of a Failing 1998-1999 GMC 3500 PCM
- ✔ Check Engine Light: The light is on, and you may have codes related to module communication, sensor circuits, or processor faults.
- ✔ No-Start or Hard Starting: The engine cranks but won’t start, or takes an excessive amount of time to fire up.
- ✔ Stalling: The engine randomly stalls while driving or idling for no apparent reason.
- ✔ Poor Engine Performance: You may notice a significant loss of power, hesitation during acceleration, or rough idling.
- ✔ Reduced Fuel Economy: A faulty PCM can’t properly manage the engine’s fuel delivery, leading to a noticeable drop in MPG.
- ✔ Erratic Transmission Shifting: The transmission may shift harshly, at the wrong times, or not shift at all, as the PCM also controls its functions.
- ✔ Communication Issues: Your OBD-II scan tool may be unable to connect to the vehicle’s computer.
A Simple, Programmed Solution
Don’t let a faulty engine computer keep your reliable GM truck off the road. This replacement PCM is a cost-effective and dependable solution. The process is straightforward: after your purchase, simply provide us with your vehicle’s VIN. Our technicians will then flash the module with the correct software for your specific make, model, engine, and transmission. This means the computer arrives at your door ready for installation, saving you a costly trip to the dealership for programming.
This module is a direct fit for a wide range of 1998-1999 General Motors trucks, vans, and SUVs. It is a compatible replacement for multiple part numbers, including 09355699, 16266645, 9355699, 16250279, 16258815, 09366810, and 9366810. Please verify the part number on your original module and consult the detailed fitment list to ensure compatibility.
Please Note: While this PCM comes programmed to your VIN, many GM vehicles of this era require a security relearn procedure after installation. This is a simple process that can typically be done without special tools and involves a sequence of key cycles. Instructions for this procedure are widely available online or in service manuals.
Frequently Asked Questions
What information do I need to provide for programming?
We require your vehicle’s 17-digit Vehicle Identification Number (VIN). This is typically found on your driver’s side dashboard (visible through the windshield), your door jamb sticker, or on your vehicle’s registration and insurance documents.
Is this a plug-and-play part?
Almost. It is pre-programmed to your VIN, so it will control the engine and transmission correctly. However, you will likely need to perform a security relearn procedure (often called a VATS or Passlock relearn) to allow the vehicle to start. This procedure typically takes about 30 minutes and does not require a scan tool.
Will this fix my check engine light?
If the check engine light and associated codes are being caused by a faulty PCM, then yes, this replacement part will resolve the issue. It’s crucial to properly diagnose the problem first, as the light could be on for other reasons like a bad sensor.
This part is used. How do I know it’s reliable?
Every module we sell is sourced from a salvaged vehicle and undergoes rigorous testing on a specialized bench to ensure all circuits and processors are functioning correctly. We guarantee its performance and back it with our warranty.
Do I need to send my old computer back?
No core charge or return is required for this particular part. You can keep or dispose of your old module as you see fit.