If you’re dealing with frustrating, hard-to-diagnose issues on your GMC Envoy or other GM vehicle, the Powertrain Control Module (PCM) is often the culprit. As a technician with over two decades of experience, I’ve seen firsthand how a failing PCM can cause a cascade of problems that seem unrelated—from erratic shifting and poor fuel economy to a vehicle that won’t start at all. This isn’t just a part; it’s the central command center for your engine and transmission, and when it fails, your vehicle’s reliability is gone.
This is your direct, reliable solution. We are offering a genuine replacement Powertrain Control Module, compatible with part number 16265035. The most significant benefit we provide is our professional programming service. Before we ship the module, we will flash it with the latest GM software updates using the specific Vehicle Identification Number (VIN) from your truck or van. This critical step ensures the PCM communicates perfectly with your vehicle’s systems right out of the box, eliminating the need for an expensive trip to the dealership for programming.
Case Study: The Ghost in the Machine
I remember a 1999 GMC Jimmy with the 4.3L V6 that came into the shop with a classic “ghost” problem. The owner said it would randomly stall at stoplights, but only when warm. It would start right back up, but the check engine light would flicker and then go out. We checked fuel pressure, the ignition system, and scanned for codes—nothing consistent. After two days of diagnostics, I noticed the data stream from the PCM would freeze for a split second right before the stall. On a hunch, we swapped in a known-good, programmed PCM. The problem vanished instantly. The original PCM’s processor was failing under heat, a common issue in these units. This experience is why I stand behind providing a properly programmed 1998-2000 Envoy PCM as the definitive fix for these elusive electronic issues.
Is Your GM Truck or SUV Showing These Symptoms?
A failing PCM can manifest in many ways. If you’re experiencing any of the following, this module is likely the solution you need. Don’t let a faulty computer keep you off the road.
- ✔ Persistent Check Engine Light (CEL) that won’t clear.
- ✔ Stalling, rough idling, or difficulty starting the engine.
- ✔ Noticeable decrease in fuel mileage.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ The engine cranks but refuses to start (no-start condition).
- ✔ Failed emissions test due to module-related codes.
- ✔ Diagnostic Trouble Codes (DTCs) such as P0601, P0604, or P0606, indicating internal module failure.
A Straightforward Guide to Installation
Replacing your 1998-2000 Envoy PCM is a job most DIYers can handle with basic tools. Because we program it beforehand, you skip the hardest part. Just follow these general steps (always consult a vehicle-specific repair manual for details).
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts.
- Locate the PCM: On most of these vehicles, the PCM is located in the engine compartment, either on the driver’s side fender, near the battery, or on the passenger side firewall. Check your specific model for the exact location.
- Disconnect the Connectors: Carefully unplug the electrical wiring harnesses from the old PCM. These connectors have locking tabs that may need to be squeezed or lifted to release. Avoid pulling on the wires themselves.
- Remove the Old Module: Unbolt the old PCM from its mounting bracket. There are typically a few bolts holding it in place.
- Install the New Module: Mount your new, pre-programmed PCM onto the bracket and securely fasten the bolts.
- Reconnect Everything: Plug the wiring harnesses firmly into the new module until they click into place. Reconnect the negative battery terminal.
- Perform Security Relearn: Your vehicle’s anti-theft system (Passlock/VATS) will need to relearn the new PCM. This is a simple procedure that usually involves turning the key to the ‘ON’ position for 10-15 minutes. We will include specific instructions for this with your order.
Verified Vehicle Compatibility
This module is a direct replacement for part numbers 16263494, 16265035, 8162634940, 218-11787, and 21811787. It is guaranteed to fit the following vehicles. Please match your part number or contact us with your VIN to confirm.
CHEVROLET EXPRESS & GMC SAVANA VANS (1500/2500/3500) 1999-2002
CHEVROLET ASTRO & GMC SAFARI VANS 1999-2001
CHEVROLET S10 & GMC SONOMA 1998-2000 (4.3L)
CHEVROLET BLAZER & GMC JIMMY 1998-2000
CHEVROLET TAHOE & GMC YUKON 1999-2000
CADILLAC ESCALADE 1999-2000
OLDSMOBILE BRAVADA 1998-2000
GMC ENVOY 1998-2000
ISUZU HOMBRE 1998-2000 (4.3L)
Note: Specific options and build dates apply. Matching the ID number (e.g., 16263494) from your original module is the best way to ensure compatibility.
Frequently Asked Questions
Do I need to do anything after I install it?
Yes. While the main engine programming is done, you will need to perform a simple security relearn procedure so the module syncs with your vehicle’s anti-theft system. We provide easy-to-follow instructions for this process. It takes about 30 minutes and requires no special tools.
How do I provide my VIN?
After you complete your purchase, simply send us a message with your 17-digit VIN. We cannot program and ship your module without it. You can find your VIN on your vehicle’s registration, insurance card, or on the driver’s side dashboard near the windshield.
Is this a reliable, long-term fix?
Absolutely. We use quality modules and flash them with the latest stable software from GM. This corrects many of the original factory software bugs and provides a durable, dependable solution to your vehicle’s electronic problems.
Will this fix my transmission shifting problems?
In many cases, yes. The PCM also controls transmission functions, including shift points and line pressure. If your shifting problems are caused by a faulty computer, this module will resolve them. However, it will not fix internal mechanical issues with the transmission.
What if my part number is slightly different?
This module replaces several part numbers, including 16263494 and 8162634940. As long as your vehicle is on the compatibility list and you provide your VIN, we will ensure the programming is a perfect match for your specific application.