Is Your GM Truck or Van Suddenly Unreliable?
If you’re driving a late ’90s or early 2000s GM vehicle like a 1999 GMC 1500, you know it’s a workhorse. But when the Powertrain Control Module (PCM) starts to fail, it can feel like the truck is possessed. After two decades of diagnosing these vehicles, I’ve seen it all. The symptoms are often confusing and can lead you down a rabbit hole of replacing perfectly good sensors.
A failing PCM is the root cause of some of the most frustrating vehicle problems. It’s the brain of your engine and transmission, and when it malfunctions, the entire vehicle suffers.
Common Symptoms of a Failing GM PCM
- ✔ Check Engine Light is on with communication error codes (U-codes) or no communication with a scan tool.
- ✔ The engine cranks but won’t start, or it starts and immediately stalls.
- ✔ Harsh, erratic, or delayed transmission shifting.
- ✔ A noticeable drop in fuel economy for no apparent reason.
- ✔ The engine runs rough, misfires, or idles poorly, even after a tune-up.
- ✔ Your anti-theft or security light stays on, preventing the engine from starting.
“A customer’s 1999 GMC Sierra 1500 came in last week with these exact symptoms. It would die randomly at stoplights and sometimes refuse to restart for 10-15 minutes. The owner had already replaced the fuel pump and crank sensor. When I connected my professional scan tool, I couldn’t even communicate with the PCM—a dead giveaway. I went straight to the module, verified it had proper power and ground at the connectors, and confirmed the communication network wiring was intact. All signs pointed to an internal failure of the PCM itself. After 20+ years of heat cycles and vibration in the engine bay, the delicate internal circuits had simply given out. This is a story I’ve seen play out hundreds of times on these specific GM trucks and vans.”
The Plug-and-Play Solution: Programmed to Your VIN
Replacing the PCM used to mean a trip to the dealership for expensive programming. Not anymore. This module, part number 21811787, is the definitive, hassle-free solution. We take the guesswork and extra cost out of the equation.
Here’s how it works:
- ✔ Provide Your VIN: After you place your order, you’ll provide us with your vehicle’s 17-digit Vehicle Identification Number (VIN).
- ✔ We Handle the Programming: Using that VIN, my team flashes the module with the latest, most stable software directly from GM. This ensures the PCM has the correct calibration for your specific engine, transmission, and options.
- ✔ Install and Drive: The module arrives at your door ready for installation. Simply disconnect the battery, swap the old module with this one, reconnect the battery, and perform the security relearn procedure (if required for your model). No special tools, no dealer visit.
Guaranteed Compatibility
This Electronic Control Module is a direct replacement for a wide range of GM vehicles and is compatible with several original part numbers. Verifying your part number is the best way to ensure a perfect fit. This module replaces:
- ✔ 16263494
- ✔ 16265035
- ✔ 8162634940
- ✔ 218-11787
- ✔ 21811787
This part fits dozens of models, including the Chevrolet Silverado, GMC Sierra, Tahoe, Yukon, Suburban, S10/Sonoma, Blazer/Jimmy, Express/Savana vans, and more from approximately 1998-2002. Please consult the detailed fitment list to confirm it’s the right part for your truck or van. Don’t let a faulty computer keep your reliable GM vehicle off the road. This is the expert-approved, straightforward fix you’ve been looking for.