Get Your GM Truck or Van Running Right Again
Is your 1998-1999 Express 2500 Van acting up? If you’re dealing with a frustrating no-start condition, a persistent check engine light, rough idling, or erratic transmission shifting, a failing Powertrain Control Module (PCM) is often the culprit. As the brain of your vehicle’s engine and transmission, when the PCM goes, it can cause a host of problems that seem impossible to pin down. This isn’t just an inconvenience; for a workhorse like an Express van, downtime means lost time and money.
This is a reliable, tested PCM, part number 16266645, that serves as a direct-fit replacement for a wide range of GM vehicles. The best part? We take the biggest headache out of the repair. Simply provide us with your vehicle’s VIN (Vehicle Identification Number) after your purchase, and our technicians will program the module with the latest GM software updates specifically for your vehicle. This means it arrives at your door ready to install, saving you a costly trip to the dealership and their programming fees. Restore your vehicle’s performance and dependability with a solution designed to get you back on the road quickly.
Case Study: A Tricky Diagnosis
A few months back, a 1999 Suburban came into my bay with a complaint of a random, hard 1-2 shift and an intermittent stall at red lights. The owner had already replaced the throttle position sensor and cleaned the MAF sensor, but the problem persisted. No specific transmission codes were stored, only a generic P0300 random misfire code. After checking fuel pressure and spark, everything looked fine. On a hunch, I monitored the live data stream from the PCM and noticed the torque converter clutch command was flickering erratically. This pointed directly to an internal PCM fault. We installed one of these pre-programmed PCMs, and the truck has been running perfectly ever since. Sometimes, the problem isn’t mechanical—it’s the computer making the decisions.
Is Your Vehicle Showing These Symptoms?
A failing PCM can manifest in many ways. If you’re experiencing any of the following, this module is the likely solution for your 1998-1999 Express 2500 PCM issues.
- ✔ Check Engine Light is on with codes like P0601 (Internal Control Module Memory Check Sum Error) or P0606 (PCM Processor Fault).
- ✔ The engine cranks but refuses to start.
- ✔ Poor or declining fuel economy.
- ✔ Harsh or unpredictable automatic transmission shifting.
- ✔ Intermittent stalling or engine hesitation.
- ✔ Failure to pass an emissions inspection.
- ✔ Loss of communication with the diagnostic scan tool.
A Straightforward Guide to Installation
Installing your programmed 1998-1999 Express 2500 PCM is a manageable job for a DIYer with basic tools. Follow these steps carefully.
- Safety First: Disconnect the negative terminal from your vehicle’s battery and secure it away from the post to prevent accidental reconnection.
- Locate the PCM: On most of these 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 Harnesses: Carefully unclip and remove the electrical wiring harnesses connected to the old PCM. These connectors have locking tabs that may need to be gently pried up.
- Remove the Old Module: Unbolt the old PCM from its mounting bracket. Keep the hardware, as you may need it for the new installation.
- Install the New PCM: Mount your new, pre-programmed PCM onto the bracket and secure it with the bolts.
- Reconnect Everything: Firmly plug the wiring harnesses into the new module. You should hear a click as they lock into place. Reconnect the negative battery terminal.
- Security Relearn Procedure: In many cases, you will need to perform a security relearn procedure. This typically involves turning the key to the ‘ON’ position for 10-15 minutes, then ‘OFF’ for 10 seconds, and repeating this cycle three times. This allows the vehicle’s anti-theft system to recognize the new PCM.
Verified Vehicle Compatibility
This module is a direct replacement for service number 16266645 and interchanges with part numbers 09355699, 9355699, 16250279, 16258815, 09366810, and 9366810. It is guaranteed to fit the following vehicles, provided the ID on your original module is 9355699:
Fits a wide range of 1998-1999 GM models including Chevrolet/GMC 1500, 2500, & 3500 Pickups; Express & Savana Vans; Suburban, Tahoe, Yukon, Escalade; Astro & Safari Vans; S10/S15/Sonoma, Blazer/Jimmy, Bravada, Envoy; and the Isuzu Hombre with the 4.3L V6. Please verify the ID number on your current module to ensure perfect compatibility.
Frequently Asked Questions
Why do you need my VIN?
Your Vehicle Identification Number (VIN) is essential. It allows our technicians to program the PCM with the exact software and calibrations your specific vehicle requires, including engine size, transmission type, and any factory options. This ensures seamless integration and performance.
Is this a plug-and-play part?
Yes, because we program it to your VIN before shipping, it is a plug-and-play solution. In some cases, a simple security relearn procedure (as outlined in the installation guide) is required, which does not need any special tools.
Is this a new part?
No, this is a high-quality, tested used part sourced from a salvaged vehicle. Each unit is inspected and verified to be fully functional before being programmed and shipped.
Will this fix my check engine light?
If the check engine light is caused by an internal failure of the original PCM (like codes P0601-P0606), then yes, this will resolve the issue. However, you should always ensure other potential problems (sensors, wiring) have been properly diagnosed first.
What if I order the wrong part?
We strongly encourage you to match the part number (16266645) or the compatible ID (9355699) from your old module before ordering. If you are unsure, please contact us with your VIN, and we will be happy to verify fitment for you.