Is Your Chevy Express Van Running Rough? The PCM Might Be the Culprit.
The Powertrain Control Module (PCM), often called the Engine Control Module (ECM), is the central computer of your 1998-1999 Chevrolet Express 2500 Van. It manages critical functions like fuel delivery, spark timing, transmission shifting, and emissions controls. When this vital component begins to fail, it can trigger a cascade of confusing and frustrating symptoms, from a persistent check engine light to a vehicle that won’t start at all. If you’re dealing with erratic performance, this pre-programmed PCM is the reliable, straightforward solution you need to get your workhorse back on the road.
From the Diagnostic Bay
We had a 1999 Savana 2500 (which uses the same PCM) come into the shop with a random misfire code that just wouldn’t go away. The owner had already replaced the spark plugs, wires, cap, and rotor. He was convinced it was a mechanical issue. After hooking up our diagnostic scanner and monitoring live data, we noticed the fuel trim on one bank was completely erratic. A deeper dive showed the injector driver circuit for cylinder #3 was failing intermittently inside the PCM itself. It wasn’t a bad injector; it was the computer telling it what to do. A new, programmed PCM like this one solved the problem in under 20 minutes. It’s a classic case of a faulty module mimicking a mechanical or sensor failure.
Common Symptoms of a Failing 1998-1999 Express 2500 PCM
A failing powertrain control module can manifest in various ways. If you’re experiencing any of the following issues, it’s a strong indicator that your PCM needs replacement. Ignoring these signs can lead to further damage to your engine or transmission, poor fuel economy, and failed emissions tests.
- ✔ Persistent Check Engine Light (CEL) with codes related to internal processor errors or sensor circuits.
- ✔ Unexplained engine stalling or stumbling, especially when warm.
- ✔ Rough or erratic idling that doesn’t improve with a standard tune-up.
- ✔ Harsh, delayed, or incorrect transmission shifting.
- ✔ A noticeable drop in fuel efficiency.
- ✔ The engine cranks but refuses to start, even with good fuel pressure and spark.
- ✔ Communication errors with diagnostic scan tools.
A Plug-and-Play Solution Programmed for Your Van
The biggest hurdle in replacing a modern vehicle computer is the programming. This module eliminates that obstacle. We take a reliable, tested, used OEM unit and flash it with the latest official GM software specifically for your vehicle. All you need to do is provide us with your van’s 17-digit Vehicle Identification Number (VIN) during checkout. This ensures that the module communicates perfectly with your van’s engine, transmission, and other systems right out of the box. No expensive trips to the dealership for programming are necessary.
This module, part number 16266645, is a direct replacement for a wide range of GM trucks and vans from this era, including the Chevrolet Express, GMC Savana, Chevrolet/GMC Pickups, Tahoe, Yukon, and more. It is compatible with multiple service numbers, including 09355699, 16250279, and 9366810.
Frequently Asked Questions
Do I need to program this PCM?
No. This PCM comes pre-programmed to your vehicle’s specific VIN. Simply provide your VIN at checkout, and we handle all the flashing before it ships. It’s designed to be a plug-and-play installation.
Where is the PCM located on my 1998-1999 Express Van?
On the 1998-1999 Express and Savana vans, the PCM is typically located in the engine compartment, on the left-hand (driver’s) side, often near the battery or firewall.
Is this a new part?
This is a high-quality, used OEM part sourced from a salvaged vehicle. Each unit is thoroughly inspected and tested to ensure it is fully functional before being programmed and shipped.
What is a VIN and why do you need it?
The VIN is your vehicle’s unique 17-digit serial number. We use it to load the exact factory software and calibrations for your van’s specific engine, transmission, and options, ensuring perfect compatibility.
Will this fix my check engine light?
If the check engine light is caused by an internal failure of your original PCM, then yes, this part will resolve the issue. However, you should always have your vehicle properly diagnosed to ensure the PCM is the root cause and not a faulty sensor or wiring problem.