Restore Your Workhorse: The Right PCM for Your 1998-1999 GMC 3500
If you’re dealing with frustrating engine problems in your late-90s GM truck or van, you know how quickly a reliable workhorse can become a driveway ornament. Intermittent stalling, poor fuel economy, a persistent check engine light, or erratic transmission behavior often point to one culprit: a failing Powertrain Control Module (PCM). As a technician with over two decades of experience under the hood, I’ve seen firsthand how a faulty PCM can mimic a dozen other issues, leading to wasted time and money on unnecessary parts. This isn’t just a component; it’s the central command center for your vehicle’s engine and transmission.
This is a dependable, tested, and used OEM PCM, part number 16266645, pulled from a salvaged vehicle. The real value here is our in-house programming service. Before we ship it, we flash the module with the latest official GM software updates, tailored specifically to your vehicle using its unique VIN. This eliminates the need for an expensive trip to the dealership for programming. You get a part that’s ready to install right out of the box, restoring the performance and reliability you depend on. Getting your hands on a quality, correctly programmed 1998-1999 GMC 3500 PCM is the most critical step to resolving complex electronic issues and getting your truck back to work.
From the Diagnostic Bay: The Ghost in the Machine
I remember a 1999 Chevy Suburban that came into the shop with a complaint of random stalling and harsh 1-2 shifts. The owner had already replaced the fuel pump and a few sensors with no luck. The codes were all over the place—O2 sensor codes, a random misfire, and a transmission communication code. After checking the wiring and grounds, my experience pointed straight to the PCM. These specific GM modules can develop internal connection failures from years of heat cycles. We installed a VIN-programmed PCM just like this one, and it was like flipping a switch. The truck ran perfectly, all the ghost codes vanished, and the transmission shifted smoothly. It’s a classic case where the ‘brain’ was the problem, not the ‘body’.
Is Your Truck Showing These Warning Signs?
A failing PCM can cause a wide range of symptoms. If you’re experiencing any of the following, a replacement module is often the solution:
- ✔ Check Engine Light is on with codes like P0601 (Internal Control Module Memory Check Sum Error) or other communication errors.
- ✔ The engine cranks but won’t start.
- ✔ Unexplained drops in fuel economy.
- ✔ The transmission shifts harshly, late, or not at all.
- ✔ Intermittent stalling or rough idling.
- ✔ Failure to pass an emissions test.
- ✔ Communication issues with your scan tool.
Your Straightforward PCM Installation Guide
Installing your pre-programmed 1998-1999 GMC 3500 PCM is a manageable job for a DIYer with basic tools. Follow these steps carefully for a smooth installation.
- Safety First: Disconnect the negative terminal from your vehicle’s battery and secure it away from the post to prevent accidental contact.
- Locate the PCM: On most 1998-1999 GM trucks and vans, the PCM is located in the engine compartment, typically on the driver’s side fender well or near the battery.
- Disconnect the Connectors: Carefully unplug the wiring harness connectors from the old PCM. These connectors have locking tabs that may need to be lifted or squeezed to release. Do not force them.
- Remove the Old Module: Unbolt the PCM from its mounting bracket. There are usually two or three bolts holding it in place.
- Install the New Module: Mount your new, pre-programmed PCM onto the bracket and secure it with the bolts.
- Reconnect Everything: Firmly plug the wiring harness connectors into the new PCM until they click into place. Reconnect the negative battery terminal.
- Security Relearn (If Necessary): In some cases, a security relearn procedure may be required. This can typically be done without special tools by cycling the key. We include instructions for this simple process if it applies to your vehicle.
Verified Compatibility for Your GM Vehicle
This module, identified by service ID 9355699, is a direct replacement for part number 16266645 and other interchangeable numbers. It is guaranteed to fit the following gasoline-engine models. Please match your vehicle and options below:
- ✔ Chevrolet/GMC 1500, 2500, & 3500 Pickups (1998-1999)
- ✔ Chevrolet Suburban & Tahoe / GMC Yukon (1998-1999)
- ✔ Cadillac Escalade (1999)
- ✔ Chevrolet Express & GMC Savana Vans 1500, 2500, 3500 (1998-1999)
- ✔ Chevrolet Astro & GMC Safari Vans (1998)
- ✔ Chevrolet S10 / GMC Sonoma (1998, 4.3L)
- ✔ Chevrolet Blazer / GMC Jimmy (1998, 4.3L)
- ✔ Oldsmobile Bravada (1998, 4.3L)
- ✔ Isuzu Hombre (1998, 4.3L)
Note: This is a comprehensive list. The key is matching the service ID 9355699 on your original module. This ensures perfect compatibility for your specific 1998-1999 GMC 3500 PCM replacement.
Frequently Asked Questions
What do I need to do after I buy this PCM?
After your purchase, you must send us your vehicle’s 17-digit VIN (Vehicle Identification Number). We cannot program and ship the module without it. You can typically find your VIN on your dashboard (visible through the windshield) or on the driver’s side door jamb sticker.
Is any other programming required after installation?
No. Because we program the PCM to your VIN before shipping, it arrives ready to install. In some vehicles, a simple security relearn procedure (which takes about 30 minutes and involves cycling the ignition key) may be needed. We provide easy-to-follow instructions for this.
Is this a new part?
No, this is a high-quality, tested used OEM part sourced from a salvaged vehicle. This provides OEM reliability at a significant cost savings compared to a new dealer part.
How do I know if this part number will fit my truck?
This module is compatible with several part numbers, including 16266645, 09355699, 16250279, and more. The most important identifier is the service ID ‘9355699’ on your original module’s sticker. If it matches, this part will work for your vehicle.
What if I install it and still have problems?
While this PCM will solve issues caused by a faulty module, it won’t fix other mechanical or electrical problems (like bad sensors or wiring). We recommend ensuring your vehicle’s core issues have been properly diagnosed. We guarantee the module itself is functional and correctly programmed.