Is Your GM Workhorse Suddenly Unreliable?
If your 1999-2002 Chevrolet Express 2500, or another trusty GM truck or van from that era, is suddenly giving you headaches, the Powertrain Control Module (PCM) is often the culprit. As a mechanic with over two decades of experience, I’ve seen these symptoms countless times. You might be dealing with a van that refuses to start on a cold morning, stalls for no reason at a stoplight, or shifts gears so harshly it feels like you’ve been rear-ended. These aren’t just annoyances; they’re signs that the brain of your vehicle’s engine and transmission is failing.
The PCM is responsible for managing everything from fuel injector timing and spark delivery to transmission shift points and torque converter lockup. After 20+ years of heat cycles, vibrations, and constant electrical processing, the delicate internal circuits can degrade, leading to a host of confusing and intermittent problems.
The Right Solution: A VIN-Programmed PCM
Simply swapping in a used module from a junkyard is a recipe for disaster. These vehicles use a sophisticated anti-theft system (GM’s Passlock or VATS) and have dozens of potential software variations based on engine size, transmission type, and emissions equipment. This is where our service stands out. We take the guesswork and frustration out of the repair.
This is a direct-fit replacement PCM compatible with part number 16265035. Before we ship it, we program it specifically to your vehicle’s 17-digit VIN. This process loads the correct, GM-certified software and calibrations for your exact configuration, ensuring all systems communicate and function as they did from the factory. It’s a plug-and-play solution designed to get you back on the road with confidence.
Expert Pro Tip: Check Your Grounds First!
Before you condemn your PCM, I always tell my customers to do one thing: check and clean the main engine and body ground connections. On these GM trucks and vans, a corroded or loose ground strap (especially the one from the engine block to the firewall or frame) can cause low voltage issues that mimic a failing PCM. It’s a 15-minute check that has saved hundreds of my clients from an unnecessary repair. If your grounds are clean and tight and the problems persist, the PCM is your next logical step.
Common Symptoms of a Failing GM PCM:
- ✔ Check Engine Light is on with communication error codes (U-codes) or various sensor codes.
- ✔ The engine cranks but refuses to start.
- ✔ Random stalling, especially when coming to a stop or at idle.
- ✔ Harsh, erratic, or delayed transmission shifting.
- ✔ Poor fuel economy and a noticeable loss of power.
- ✔ The ‘Security’ or ‘Anti-Theft’ light stays on, preventing the engine from starting.
- ✔ Inaccurate or non-functional instrument cluster gauges.
Installation and Post-Install Procedure
Physically replacing the PCM is straightforward. On most Express and Savana vans, it’s located in the engine compartment on the driver’s side, near the battery. After installation, you will need to perform a security relearn procedure, which can typically be done without special tools and takes about 30 minutes. We include instructions for this. For optimal transmission performance, a Crankshaft Position System Variation (CASE) relearn is recommended using a compatible bi-directional scan tool, though the vehicle will run and drive without it.
This Module is a Direct Replacement For:
- ✔ Part Numbers: 16263494, 16265035, 8162634940, 218-11787, 21811787
- ✔ A wide range of GM trucks and vans from approximately 1998-2002. Please verify your part number and check the detailed fitment list to ensure compatibility.