If your trusty GMC 3500 is suddenly stalling, shifting erratically, or just won’t start, the problem often points to the very brain of the operation: the Powertrain Control Module (PCM). As a technician with over two decades of experience, I’ve seen countless owners chase expensive sensor and component replacements when the root cause was a failing PCM. This isn’t just a part; it’s the central command for your truck’s engine and transmission, and when it falters, the symptoms can be confusing and frustrating.
We’re offering a reliable, cost-effective solution. This is a tested, genuine GM Powertrain Control Module, part number 16258815, sourced from a salvaged vehicle. The biggest hurdle with replacing a PCM has always been the expensive trip to the dealership for programming. We eliminate that step entirely. Simply provide us with your vehicle’s VIN at checkout, and we will flash this computer with the latest official GM software updates specific to your truck. It arrives at your door ready for a straightforward installation, saving you time and hundreds of dollars in dealer fees.
From the Diagnostic Bay: The Ghost in the Transmission
A customer brought in his ’99 Chevy 2500—a nearly identical system to your GMC—convinced his 4L80E transmission was shot. It was slamming into gear and refusing to shift into overdrive. He’d already spent a small fortune on a new filter, fluid, and shift solenoids with no luck. I hooked up my scan tool and saw no specific transmission codes, just a generic P0601 (Internal Control Module Memory Check Sum Error). After verifying the wiring was solid, I knew the PCM was the culprit. It wasn’t sending the right signals to the transmission. We swapped in a pre-programmed PCM just like this one, performed the quick CASE relearn, and the truck shifted like it just rolled off the factory floor. He saved thousands by not replacing a perfectly good transmission.
Is Your Truck Showing These Symptoms?
A faulty PCM can manifest in numerous ways. If you’re experiencing any of the following, this module is a likely and effective solution:
- ✔ Persistent Check Engine Light (CEL) with codes like P0601, P0604, or P0606
- ✔ Engine stalling, stumbling, or refusing to start
- ✔ Noticeable decrease in fuel economy
- ✔ Harsh or erratic automatic transmission shifting
- ✔ Failure to pass an emissions or smog test
- ✔ Intermittent issues that mechanics can’t seem to diagnose
A Straightforward Guide to Installation
Installing your pre-programmed 1998-1999 GMC 3500 PCM is a job most DIYers can handle in under an hour. While a security relearn might be necessary, the core installation is simple.
- Safety First: Disconnect the negative terminal from your truck’s battery to prevent any electrical shorts.
- Locate the PCM: On most of these GMT400 trucks and vans, the PCM is located in the engine compartment, typically on the driver’s side fender well.
- Disconnect the Harnesses: Carefully unclip and remove the electrical connectors. There are usually several color-coded connectors with locking tabs. Do not force them.
- Remove the Old Module: Unbolt the mounting bracket holding the old PCM in place and remove it from the vehicle.
- Install the New Module: Mount your new, pre-programmed PCM, reconnect the wiring harnesses securely, and re-attach the negative battery terminal.
- Perform Relearn Procedure: In many cases, you will need to perform a Crankshaft Variation (CASE) relearn and/or a security relearn. This can often be done with a capable bi-directional scan tool or by following a specific key-cycle procedure. This step is critical for optimal performance.
Why Choose Our VIN-Programmed PCM?
This isn’t just a used part pulled from a yard. It’s a complete solution. By programming the 1998-1999 GMC 3500 PCM to your specific VIN, we ensure it communicates perfectly with your truck’s other modules, anti-theft system, and specific options. The included GM software updates can resolve common drivability issues that were present from the factory, restoring performance and reliability you may not have experienced in years. Get your workhorse back on the road with confidence.
Verified Vehicle Compatibility
This module, identified by service number 16258815 or interchange ID 9355699, is a direct fit for a wide range of GM trucks and vans. Please verify your part number or consult the list below. This computer will fit these part numbers: 09355699, 16266645, 9355699, 16250279, 16258815, 09366810, 9366810.
Fits models such as: 1998-1999 Chevy & GMC 1500/2500/3500 Pickups (Gasoline), 1998-1999 Suburban/Tahoe/Yukon (Gasoline), 1998-1999 Express & Savana 1500/2500/3500 Vans (Gasoline), 1999 Cadillac Escalade, 1998 Astro/Safari, 1998 Blazer/Jimmy S-15, 1998 S10/S15/Sonoma (4.3L), 1998 Bravada, 1998 Envoy, and 1998 Isuzu Hombre (4.3L). Please match your service ID for guaranteed compatibility.
Frequently Asked Questions
Do I need to do any programming myself?
No. We handle the main programming. Just provide your VIN during checkout, and we will flash the module with the latest GM software for your vehicle. It arrives ready to install.
What is a CASE Relearn and will I need to do it?
A CASE (Crankshaft Position System Variation) relearn synchronizes the PCM with the crankshaft position sensor. It is highly recommended after PCM replacement to prevent a P1336 trouble code and ensure accurate misfire detection. This typically requires a bi-directional scan tool.
Is this a new part?
No, this is a high-quality, tested used OEM part sourced from a salvaged vehicle. This allows us to provide a reliable, genuine GM component at an affordable price.
Where do I find my VIN?
Your 17-digit Vehicle Identification Number (VIN) can be found on your vehicle’s registration, insurance card, or on a plate on the driver’s side of the dashboard, visible through the windshield.
What if my original part number isn’t 16258815?
This module is a direct replacement for several part numbers, including 09355699, 16266645, and others listed above. As long as your vehicle is on the compatibility list and your original module has one of these numbers, it will work correctly.