Is your GMC Envoy, Chevy Blazer, or S10 pickup acting possessed? Erratic idling, harsh shifting, a persistent check engine light, or even a no-start condition can often be traced back to a single component: a failing Powertrain Control Module (PCM). As the central computer of your vehicle, the PCM is responsible for managing everything from fuel injection and spark timing to transmission shift points. When it starts to fail, it can cause a cascade of frustrating and difficult-to-diagnose issues. Stop chasing symptoms and address the root cause with our direct-fit, pre-programmed PCM.
This isn’t just a generic, off-the-shelf part. We take the guesswork and hassle out of the replacement process. Before we ship your module, our technicians will flash it with the latest official GM software updates, specifically calibrated to your vehicle using the VIN you provide. This ensures optimal performance, fuel efficiency, and emissions compliance, effectively restoring your vehicle’s factory-new operational parameters. This critical programming step saves you a costly trip to the dealership and eliminates the need for specialized scan tools, making this a straightforward solution for both DIY mechanics and professional shops.
Common Symptoms of a Failing GM PCM
- ✔ Check Engine Light: The check engine light is illuminated, often with communication error codes (U-codes) or codes related to multiple, unrelated sensors.
- ✔ Engine Performance Issues: You may experience stalling, rough idling, hesitation during acceleration, misfires, or a noticeable decrease in power.
- ✔ Poor Fuel Economy: A faulty PCM can’t properly manage the air-fuel mixture, leading to a sudden and significant drop in your vehicle’s gas mileage.
- ✔ Transmission Problems: The PCM also controls automatic transmission functions. A failing module can cause hard shifting, delayed engagement, or getting stuck in one gear (limp mode).
- ✔ Vehicle Won’t Start: In cases of complete failure, the PCM may not be able to activate the fuel pump or ignition coils, resulting in a crank-no-start situation.
- ✔ Failed Emissions Test: Incorrect engine management will almost certainly lead to a failed smog or emissions inspection.
From the Diagnostic Bay
We had a 1999 Chevy S10 with the 4.3L V6 come into the shop that was driving the owner crazy. The truck would run fine for days, then suddenly start shifting hard and the speedometer would drop to zero while driving. He had replaced the vehicle speed sensor (VSS) twice with no luck. We scanned it and found no hard codes, just a history of lost communication with the transmission module. After checking the wiring harness and finding no issues, we suspected the PCM. These early GM PCMs are notorious for developing internal connection issues over time. We installed a VIN-programmed PCM, performed the security relearn, and the truck’s gremlins were gone for good. It’s a classic case where the symptoms seem to point elsewhere, but the root cause is the vehicle’s central computer.
Your Direct-Fit 1998-2000 Envoy PCM Solution
This module is the definitive solution for a wide range of popular GM trucks, vans, and SUVs from the late 1990s and early 2000s. By replacing your old, failing computer, you restore the precise calculations needed for your engine and transmission to work in harmony. Our pre-programming service is what sets this part apart. You receive a module that is ready to be installed, requiring only a simple security relearn procedure that you can perform yourself in your driveway—no special tools needed. This module is a direct replacement for multiple part numbers, including 16263494, 16265035, and 8162634940. Ensure you match one of these numbers from your original module for guaranteed compatibility.
Please Note: After installation, a security relearn procedure (often called Passlock or VATS relearn) is required. This pairs the new PCM to your vehicle’s anti-theft system. The procedure typically involves cycling the key in the ignition and takes about 30 minutes to complete. We include instructions to make this process simple.
Frequently Asked Questions
Do I need to have this module programmed by a dealer?
No. We program the module for you before it ships. Simply provide us with your vehicle’s 17-digit VIN during or after checkout, and we will flash the unit with the correct GM calibration for your specific vehicle.
What is a security relearn and is it difficult?
A security relearn is a simple procedure that syncs the new PCM with your vehicle’s anti-theft system. It’s required for the vehicle to start. The process typically involves turning the key to the ‘ON’ position for 10 minutes, then ‘OFF’ for 10 seconds, and repeating this sequence three times. It’s an easy procedure that requires no tools, and we provide clear instructions.
How do I find my vehicle’s VIN?
Your Vehicle Identification Number (VIN) can be found on a metal tag on the driver’s side of the dashboard (visible through the windshield), on the driver’s side door jamb sticker, or on your vehicle’s registration and insurance documents.
Is this PCM compatible with models other than the GMC Envoy?
Yes, absolutely. This PCM is used in a very wide range of GM vehicles from that era, including the Chevy S10, Blazer, Silverado, Express Van, GMC Jimmy, Sonoma, Sierra, Savana Van, and Oldsmobile Bravada, among others. Please check the detailed fitment list on this page and match your original part number to ensure compatibility.
What happens if I install this without providing a VIN?
The module will not have the correct software for your vehicle’s engine, transmission, and options. This will result in poor performance, a check engine light, and potentially a no-start condition. Providing your VIN is essential for a successful repair.