Is Your GMC Truck Running Rough? The PCM Might Be the Culprit.
If your 1999 GMC 1500 is experiencing frustrating issues like a persistent check engine light, poor fuel economy, erratic shifting, or even a no-start condition, a failing Powertrain Control Module (PCM) is often the root cause. As the central computer for your truck’s engine and transmission, the PCM is responsible for managing everything from fuel injection and ignition timing to transmission shift points. When it fails, the symptoms can be widespread and difficult to diagnose, leading to wasted time and money on unnecessary repairs.
From the Diagnostic Bay
We had a customer with a ’99 Sierra who had replaced nearly every sensor under the hood—O2 sensors, MAP sensor, TPS—chasing a stubborn rough idle and stalling issue. The check engine light would come on with a random assortment of codes that didn’t point to a single component. After confirming all the new sensors were working, we finally tested the PCM’s driver circuits and found they were failing intermittently. A new, properly programmed PCM solved all the issues instantly. It’s a classic case of treating the symptoms instead of the disease; sometimes, the problem lies with the brain itself.
Common Symptoms of a Failing PCM
- ✔ Check Engine Light is on with various, often unrelated, trouble codes.
- ✔ Your truck fails to start or stalls unexpectedly.
- ✔ Noticeable decrease in fuel efficiency.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ Engine misfires, stumbles, or runs poorly.
- ✔ Failure to pass an emissions inspection.
Why Choose Our Pre-Programmed 1999 GMC 1500 PCM?
This isn’t just a replacement part; it’s a complete, ready-to-install solution. We eliminate the biggest hurdle in replacing a modern vehicle computer: programming. When you order from us, we use the Vehicle Identification Number (VIN) you provide to flash the module with the latest, most stable software updates directly from General Motors. This ensures that the PCM is a perfect match for your truck’s specific configuration, including its engine, transmission, and emissions equipment.
This direct-fit, VIN-programmed module saves you a trip to the dealership and the high costs associated with their programming services. The process is simple: place your order, provide us with your VIN, and we’ll ship a module that’s ready to be installed right out of the box. In many cases, after installation, the vehicle will start and run perfectly. Some vehicles may require a simple security relearn procedure, which can often be performed without special tools.
Broad Compatibility Across the GM Lineup
While this is the correct computer for a 1999 GMC 1500 PCM, part number 16263494 was a workhorse for GM, used across a wide range of trucks and vans. It is a direct replacement for part numbers 16265035, 8162634940, 218-11787, and 21811787. It fits many popular models from 1998 to 2002, including the Chevrolet Silverado, Tahoe, Suburban, S10, Blazer, and Express van, as well as the GMC Sierra, Yukon, Sonoma, Jimmy, and Savana van. Please verify the part number on your original module or consult the detailed fitment list to ensure compatibility.
Frequently Asked Questions
Do I need to get this PCM programmed?
No. We handle all the programming for you before shipment. Simply provide your vehicle’s VIN during or after checkout, and we will flash the module with the latest GM software specific to your truck.
Where do I find my vehicle’s VIN?
Your 17-digit Vehicle Identification Number (VIN) can be found on a metal plate on the driver’s side dashboard (visible through the windshield), on the driver’s side door jamb sticker, or on your vehicle’s registration and insurance documents.
Will this fix my check engine light?
If the check engine light and associated diagnostic trouble codes (DTCs) are caused by a faulty PCM, then this replacement part will resolve the issue. It is crucial to have your vehicle properly diagnosed to confirm the PCM is the point of failure before ordering.
Is any additional setup required after I install it?
In many cases, the vehicle will start and run correctly immediately. However, some GM vehicles of this era may require a security relearn or a Crankshaft Variation (CASE) relearn procedure. These procedures can often be completed without specialized scan tools.
Where is the PCM located on my 1999 GMC 1500?
On most 1999 GMC/Chevy 1500, 2500, and 3500 series trucks, the Electronic Control Module is located in the engine compartment on the driver’s side, often near the battery or firewall.