Restore Peak Performance to Your GMC Truck
Is your reliable 1998-1999 GMC 1500 pickup suddenly giving you headaches? If you’re dealing with a frustrating check engine light, erratic engine behavior, stalling, or poor fuel economy, the culprit is often a failing Powertrain Control Module (PCM). As a technician with over two decades of experience under the hood, I’ve seen countless GMT400 and early GMT800 trucks sidelined by PCM issues. This isn’t just a part; it’s the brain of your engine and transmission, and when it falters, your whole truck suffers. This replacement PCM is your direct, reliable solution to get your truck running like it should.
We take the guesswork and hassle out of the repair. Unlike sourcing a module from a salvage yard and then paying a dealership for expensive programming, this unit arrives at your door ready to install. We flash it with the latest official GM software updates specifically for your vehicle. All we need is your Vehicle Identification Number (VIN) after your purchase. This ensures perfect communication between the engine, transmission, and other systems, correcting factory bugs and optimizing performance from the moment you plug it in. This is the correct way to replace the brain of your truck and solve those persistent electronic gremlins for good.
A Technician’s Notebook
I remember a ’99 Sierra 5.7L that came into my bay with a complaint of intermittent stalling at stoplights and harsh, unpredictable shifting. The owner had already replaced the throttle position sensor and the idle air control valve with no luck. The scanner showed no hard codes, just a history of communication loss faults. After checking the grounds and wiring harnesses—a critical first step on these trucks—I suspected the PCM. We swapped in a pre-programmed module, performed a quick CASE relearn, and the truck ran perfectly. The internal processors on the original unit were failing under heat, causing the intermittent chaos. This replacement 1998-1999 GMC 1500 PCM prevents that diagnostic headache.
Is Your Truck Showing These Symptoms?
A failing PCM can manifest in various ways. If you’re experiencing any of the following, it’s a strong indicator that your engine computer needs replacement:
- ✔ Persistent Check Engine Light (CEL)
- ✔ Diagnostic Trouble Codes (DTCs) like P0601 (Internal Control Module Memory Check Sum Error) or P0606 (PCM Processor Fault)
- ✔ Engine stalling or randomly shutting off
- ✔ Rough or inconsistent idling
- ✔ Harsh or erratic automatic transmission shifting
- ✔ A noticeable drop in fuel mileage
- ✔ The vehicle will crank but fails to start (no-start condition)
- ✔ Failure to pass an emissions test
A Straightforward Guide to Installation
Replacing the PCM on your GMC is a manageable job for a DIYer with basic tools. Our pre-programmed module makes it even simpler. Follow these general steps to get back on the road:
- Safety First: Always disconnect the negative terminal from your truck’s battery and wait at least 15 minutes for the system capacitors to discharge.
- Locate the PCM: On most 1998-1999 GM trucks, the PCM is located in the engine bay, typically on the driver’s side fender well or near the battery.
- Disconnect Connectors: Carefully unclip and remove the large multi-pin wiring harness connectors from the old module. There are usually retaining clips or levers that need to be released. Avoid forcing them.
- Remove the Old Module: Unbolt the PCM from its mounting bracket. It’s typically held in by a few bolts (often 10mm).
- Install the New PCM: Mount your new, pre-programmed PCM onto the bracket and securely fasten the bolts.
- Reconnect Everything: Firmly plug the wiring harnesses back into the new module until they click into place. Reconnect the negative battery terminal.
- Security/CASE Relearn: In many cases, you will need to perform a security relearn procedure (often involves cycling the key) and a Crankshaft Variation (CASE) relearn, which requires a capable bidirectional scan tool. This final step is crucial for optimal engine performance and to prevent a no-start condition.
Verified Vehicle Compatibility
This module is a direct replacement for part numbers 09355699, 16250279, and 09366810. It is guaranteed to fit a wide range of GM trucks, vans, and SUVs from this era. Please verify your part number or match your vehicle from the list below:
1500/2500/3500 Pickup (1998-1999)
Astro Van (1998-1999)
Blazer S10 (1998)
Express 1500/2500/3500 Van (1998)
Suburban 1500/2500 (1998-1999)
Tahoe (1998-1999)
S10 Pickup (1998)
GMC:
1500/2500/3500 Pickup (1998-1999)
Envoy (1998)
Jimmy S15 (1998)
Safari Van (1998-1999)
Savana 1500/2500/3500 Van (1998)
Sonoma (1998)
Yukon (1998-1999)
Cadillac:
Escalade (1999)
Oldsmobile:
Bravada (1998)
Isuzu:
Hombre (1998)
Frequently Asked Questions
Why do you need my VIN?
Your VIN (Vehicle Identification Number) is essential. It allows us to load the exact, correct GM software for your truck’s specific engine, transmission, and options. This ensures seamless compatibility and optimal performance, eliminating the need for a trip to the dealer for programming.
Is this a simple plug-and-play installation?
For the most part, yes. The module is programmed for your vehicle. However, after installation, you will likely need to perform a security relearn and a Crankshaft Position (CASE) relearn. The security relearn can often be done without special tools, but the CASE relearn requires a bidirectional scan tool. This is standard for any PCM replacement on these vehicles.
Will this fix my transmission shifting problems?
If the shifting issues are caused by faulty signals or processing within the PCM, then yes, this will resolve them. The PCM controls shift points and line pressure. However, it will not fix mechanical or hydraulic problems within the transmission itself.
How do I find my original part number?
The part number is printed on a sticker on your original PCM. You can find it by locating the module in your engine bay. This unit is a direct replacement for part numbers 09355699, 16250279, and 09366810.