Programmed 1999-2000 GMC 3500 PCM 16265035 | VIN Flashed ECM

Restore Peak Performance to Your GM Truck or Van

As a technician with over two decades of experience, I’ve seen firsthand how a failing Powertrain Control Module (PCM) can bring a perfectly good truck to its knees. If your 1999-2000 GMC 3500 Pickup is suffering from baffling electrical gremlins, poor performance, or won’t start reliably, the PCM is often the culprit. This isn’t just a part; it’s the brain of your vehicle’s engine and transmission, and when it falters, everything else does too. This replacement PCM, part number 16265035, is the definitive solution to get your workhorse running like it should.

What sets this module apart is our commitment to a hassle-free repair. We don’t just ship you a box. We take your vehicle’s VIN and flash this module with the latest, most stable software directly from GM. This means it arrives at your door ready to install, saving you a costly trip to the dealership and the headache of programming fees. This is the same process we use in the shop to ensure a reliable, long-lasting fix for our customers. By choosing this pre-programmed 1999-2000 GMC 3500 PCM, you’re not just buying a part—you’re getting a complete, ready-to-go solution.

Is Your Truck Exhibiting These PCM Failure Signs?

A failing PCM can manifest in many ways, from obvious to subtle. If you’re experiencing any of the following, it’s time to consider a replacement:

• ✔ Unexplained Check Engine Light (CEL) with codes like P0601, P0604, or P0606.
• ✔ Engine stalling, stumbling, or misfiring for no apparent reason.
• ✔ Harsh or erratic automatic transmission shifting.
• ✔ The vehicle won’t start, but the battery and starter are good (intermittent no-start).
• ✔ Noticeable decrease in fuel economy.
• ✔ Failure to pass an emissions test.
• ✔ Communication errors with diagnostic scan tools.

Your Step-by-Step PCM Installation Guide

Installing your new 1999-2000 GMC 3500 PCM is a straightforward job for a confident DIYer. Follow these steps carefully for a smooth installation.

1. Safety First: Disconnect the negative terminal from your vehicle’s battery and secure it away from the post to prevent accidental contact.
2. Locate the PCM: On most of these trucks and vans, the PCM is located in the engine compartment, typically on the driver’s side fender, sometimes under the battery tray.
3. Disconnect the Wiring Harnesses: Carefully unclip and disconnect all electrical connectors from the old PCM. These connectors have locking tabs; do not force them. Inspect the connectors for any corrosion or damage.
4. Remove the Old Module: Unbolt the old PCM from its mounting bracket. Keep the hardware as you may need to reuse it.
5. Install the New Module: Mount your new, pre-programmed PCM onto the bracket and secure it with the original hardware.
6. Reconnect Everything: Firmly plug the wiring harnesses back into the new PCM until they click into place. Reconnect the negative battery terminal.
7. Perform Security Relearn (If Necessary): In many cases, you will need to perform a simple security relearn procedure. Turn the key to the ‘ON’ position for 10-15 minutes, then ‘OFF’ for 10 seconds. Repeat this cycle 3 times. On the fourth try, the vehicle should start, and the security light will be off.

Guaranteed Compatibility for Your Vehicle

This module is a direct replacement for part numbers 16263494, 16265035, 8162634940, 218-11787, and 21811787. It is confirmed to fit the following vehicles. Please verify your specific model and options.

Frequently Asked Questions About Your 1999-2000 GMC 3500 PCM