Restore Peak Performance to Your GM Truck or Van
Is your trusty 1998-1999 GMC 2500 Pickup suddenly stalling, running rough, or refusing to start? A persistent Check Engine Light that won’t go away can be incredibly frustrating. As a technician with over two decades of experience under the hood, I’ve seen these symptoms countless times. Often, the culprit isn’t a sensor or a mechanical part, but the very brain of the operation: the Powertrain Control Module (PCM). This isn’t just a part; it’s the central command for your engine’s fuel delivery, spark timing, and transmission shifts. When it fails, your vehicle’s reliability and performance suffer dramatically.
We offer a straightforward, reliable solution. This is a genuine, used GM PCM, part number 16266645, sourced from a salvaged vehicle. The critical difference is our service: before this module ships, we professionally program it with the latest GM software updates specifically for your vehicle’s VIN. This eliminates the need for an expensive trip to the dealership for programming, saving you time and money. You get a part that’s ready to be installed right out of the box, getting your workhorse back on the road where it belongs.
A Technician’s Notebook: The Intermittent No-Start
A customer brought in his ’99 Chevy Silverado 1500 with a ghost of a problem. It would start fine for a week, then suddenly refuse to crank for an hour. No rhyme or reason. He’d already replaced the battery and starter. We scanned it and found no active codes, but in the history, we saw a P0601 (Internal Control Module Memory Check Sum Error). This code is a direct indictment of the PCM itself. The internal memory was failing intermittently, causing the anti-theft system to engage randomly. We swapped in a VIN-programmed PCM just like this one, performed the security relearn, and the truck has been starting reliably ever since. It’s a classic case where chasing sensors would have been a waste of money; the core problem was the computer.
Is Your Vehicle Showing These Signs of PCM Failure?
A failing PCM can manifest in various ways. If you’re experiencing any of the following, your engine computer could be the root cause:
- ✔ Persistent Check Engine Light (CEL) with codes like P0601, P0602, P0605, or U-series communication codes.
- ✔ Engine stalling, misfiring, or running rough for no apparent reason.
- ✔ Complete no-start or intermittent starting issues.
- ✔ Noticeable decrease in fuel economy.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ Failure to communicate with a diagnostic scan tool.
A Straightforward Guide to Installation
Replacing the PCM on these GM vehicles is a job most DIYers can handle with basic tools. Here’s a general guide:
- Safety First: Always disconnect the negative terminal from your vehicle’s battery and secure it away from the post.
- Locate the PCM: On most of these trucks and vans, you’ll find the PCM in the engine compartment, typically on the driver’s side fender well or near the firewall.
- Disconnect the Harnesses: The PCM will have several large multi-pin electrical connectors. Carefully release the locking tabs and pull the connectors straight out. Avoid wiggling them, as this can damage the pins.
- Remove the Old Module: Unbolt the PCM from its mounting bracket. It’s usually held in by a few small bolts.
- Install the New PCM: Mount your new, pre-programmed PCM and securely reconnect the electrical harnesses. You should hear and feel them click into place.
- Reconnect the Battery: Reattach the negative battery terminal.
- Perform Security Relearn (If Needed): In many cases, you’ll need to perform a simple security relearn procedure. This typically involves turning the key to the ‘ON’ position for 10-15 minutes, then off, and repeating two more times. This allows the new PCM to recognize your vehicle’s keys.
Verified Vehicle Compatibility
This PCM is a direct replacement for service number 16266645 and interchanges with several other part numbers, including 09355699, 16250279, and more. It is confirmed to fit a wide range of GM vehicles. Please match your part number or verify fitment with your specific model from the list below. This unit is specifically for gasoline engines.
GMC 1500/2500/3500 PICKUP (98-99)
CHEVROLET/GMC SUBURBAN 1500/2500 (98-99)
CHEVROLET TAHOE / GMC YUKON (98-99)
CADILLAC ESCALADE (99)
CHEVROLET EXPRESS 1500/2500/3500 VAN (98-99)
GMC SAVANA 1500/2500/3500 VAN (98-99)
CHEVROLET ASTRO / GMC SAFARI (98)
CHEVROLET S10 / GMC SONOMA (98)
CHEVROLET BLAZER / GMC JIMMY (98)
OLDSMOBILE BRAVADA (98)
GMC ENVOY (98)
ISUZU HOMBRE (98)
Note: This is a partial list. Always verify fitment by the service ID number (e.g., 09355699) on your original module.
Frequently Asked Questions
What information do you need to program this PCM?
After your purchase, we require your vehicle’s 17-digit Vehicle Identification Number (VIN). This ensures we load the exact correct software and calibrations for your truck’s specific options.
Is this part truly ‘plug and play’?
Because it’s pre-programmed to your VIN, it’s as close as it gets. In most cases, you will need to perform a simple ‘Security Relearn Procedure’ which takes about 30 minutes and requires no special tools. We can provide instructions for this.
Where does this part come from?
This is a good, functional used part that has been carefully sourced from a properly dismantled, salvaged vehicle. It is tested for functionality before being programmed and shipped.
Will this fix my specific problem?
This module will resolve any issues directly caused by a faulty PCM. While it fixes many common problems, it’s essential to ensure your vehicle has been properly diagnosed. This part will not fix issues related to bad sensors, wiring, or mechanical failures.
How do I find my original part number?
Your PCM’s part number is printed on a sticker on the module itself. Look for a Service Number (SERV. NO.) like 16266645 or 09355699 to confirm a match.