Is Your GMC Truck Running Rough? The PCM Might Be the Culprit.
The Powertrain Control Module, or PCM, is the central computer of your 1999-2000 GMC 3500 Pickup. It’s the brain behind the operation, managing everything from fuel injection and ignition timing to transmission shift points and emissions controls. When this critical component begins to fail, it can cause a wide range of frustrating and often misdiagnosed problems. You might be chasing sensor codes or mechanical issues when the real problem lies with the computer itself. This replacement module is designed to restore your truck’s performance and reliability, getting you back on the road with confidence.
From the Diagnostic Bay
We once had a 2000 GMC 3500 work truck towed in that had its owner completely stumped. The complaint was a harsh 1-2 shift and a persistent check engine light for a transmission solenoid circuit. The owner, a capable mechanic himself, had already replaced the solenoid pack and checked the wiring harness for continuity, all to no avail. After hooking up our diagnostic scanner, we noticed erratic voltage readings coming from the PCM’s transmission control circuits. We installed one of our VIN-programmed modules, performed the security relearn, and the truck shifted perfectly. The internal driver for that solenoid circuit inside the original PCM had failed—a classic example of how a bad computer can mimic a mechanical failure.
Symptoms of a Failing Powertrain Control Module
A failing PCM can manifest in numerous ways. If your truck is experiencing any of the following issues, a faulty module could be to blame:
- ✔ Check Engine Light: The most common symptom. The light may be on constantly or intermittently, often with codes related to sensors, solenoids, or communication errors (U-codes).
- ✔ Poor Engine Performance: Noticeable loss of power, hesitation during acceleration, or rough idling can all point to a PCM that isn’t correctly managing the engine.
- ✔ Reduced Fuel Economy: If the PCM isn’t calculating the air-fuel mixture correctly, your truck’s gas mileage can drop significantly.
- ✔ Erratic or Harsh Shifting: The PCM also controls the transmission. A faulty module can cause delayed shifts, hard shifts, or getting stuck in one gear (limp mode).
- ✔ Engine Stalling: The engine may stall for no apparent reason, either while driving or at a stop.
- ✔ No-Start Condition: In severe cases, a complete PCM failure can prevent the engine from starting at all, even if the battery and starter are good.
Why Choose Our Programmed 1999-2000 GMC 3500 PCM?
This isn’t just a replacement part; it’s a complete, ready-to-install solution. We take the guesswork out of the repair. When you purchase this module, we use the Vehicle Identification Number (VIN) you provide to program it with the latest, most up-to-date software directly from GM. This critical step ensures that the module is a perfect match for your truck’s specific configuration, including its engine, transmission, and factory options. There’s no need for an expensive trip to the dealership for programming. For many vehicles, installation is a simple plug-and-play process, though some may require a security or CASE relearn procedure which can often be done without special tools.
This module is a direct replacement for multiple part numbers, including 16263494, 16265035, 8162634940, and 218-11787. It fits a wide variety of GM trucks and vans from the era, making it a versatile and reliable choice for your repair needs. By providing a correctly programmed 1999-2000 GMC 3500 PCM, we help you avoid the common pitfalls of installing a used, non-programmed module from a salvage yard, which can lead to compatibility issues or even damage to other vehicle components.
Frequently Asked Questions
Do I need to do any programming myself?
No. We handle all the programming before shipping. We will flash the module with the latest GM software updates using the VIN you provide, so it arrives ready to be installed in your vehicle.
Where is the PCM located on my 1999-2000 GMC 3500?
On most 1999-2000 GMC and Chevrolet pickups, the PCM (or ECM) is located in the engine compartment on the driver’s side, typically near the battery or on the inner fender.
What is a security relearn or CASE relearn?
A security relearn syncs the new PCM with your vehicle’s anti-theft system. A CASE (Crankshaft Angle Sensor Error) relearn calibrates the new PCM to the crankshaft position sensor. Many vehicles will start and run without these procedures, but they may be necessary to clear certain trouble codes or security lights. Instructions for these procedures are widely available online.
How do I provide my VIN?
After you complete your purchase, you will receive instructions on how to send us your vehicle’s 17-digit VIN. We cannot ship your part until we receive this information, as the programming is specific to your truck.
Is this a direct replacement for part number 16263494?
Yes, this module is a fully compatible, direct replacement for service number 16263494 and several other part numbers listed in the description. It is guaranteed to function correctly in vehicles that originally used any of the specified part numbers.