Get Your Workhorse Van Back on the Job, Fast.
As a technician with over two decades of experience, I know the frustration of a vehicle that won’t run right, especially when it’s your livelihood. A 1998-1999 Chevy Express 3500 Van is a dependable workhorse, but when its Powertrain Control Module (PCM) fails, it can bring everything to a halt. You’re faced with stalling, no-start conditions, or a persistent Check Engine Light that leaves you guessing. This isn’t just an inconvenience; it’s lost time and money.
This is a reliable, tested, and pre-programmed replacement PCM, part number 9355699. It’s the brain of your van’s engine and transmission, controlling everything from fuel mixture and spark timing to transmission shift points. When it falters, performance suffers. We solve this problem by taking a quality, inspected used module and flashing it with the latest official GM software updates specifically for your vehicle. All we need is your VIN. This means you get a part that’s ready to install right out of the box, saving you a costly trip to the dealership and the expense of their programming services.
A Technician’s Notebook: The Misleading Transmission Fault
I remember a 1999 Express 2500 that came into my bay with what the owner was sure was a failing transmission. It was shifting hard, erratically, and sometimes wouldn’t go into overdrive. He’d already spent money on a fluid and filter change with no improvement. After hooking up my scan tool, I noticed no specific transmission codes, but I did see a P0601 (Internal Control Module Memory Check Sum Error) from the PCM. The internal logic of the computer was failing, causing it to send corrupted commands to the transmission. We swapped in a correctly programmed PCM, and the ‘transmission problem’ vanished instantly. It’s a classic case where the root cause is electronic, not mechanical. This is a crucial diagnostic step that can save you hundreds, if not thousands, in unnecessary repairs.
Is Your Van Showing These Symptoms?
- ✔ Check Engine Light: An illuminated CEL, often with codes like P0601, P0602, P0604, or P0606, points directly to an internal PCM fault.
- ✔ Engine Stalling or No-Start: The engine may crank but refuse to start, or it might stall intermittently while driving or at idle.
- ✔ Poor Fuel Economy: A failing PCM can’t properly manage the engine’s fuel delivery, leading to a noticeable drop in MPG.
- ✔ Erratic Transmission Shifting: Harsh shifts, delayed engagement, or getting stuck in a gear can be caused by the PCM, not the transmission itself.
- ✔ Failed Emissions Test: Incorrect engine management will almost certainly lead to a failed smog check.
- ✔ Communication Issues: Your scan tool may be unable to communicate with the vehicle’s computer, a tell-tale sign of a dead PCM.
A Straightforward Guide to Installation
Replacing the 1998-1999 Express 3500 PCM is a job most DIYers can handle with basic tools. It’s located in the engine compartment, making access relatively simple.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery and wait at least 15 minutes for the system to fully discharge.
- Locate the PCM: On most Express and Savana vans, you’ll find the PCM on the driver’s side, near the battery or firewall, housed in a black plastic bracket.
- Disconnect the Connectors: Carefully unclip and remove the electrical harness connectors. They have locking tabs, so be gentle to avoid breaking them. There may be several different colored connectors.
- Remove the Old Module: Unbolt the PCM from its mounting bracket. It’s typically held in by a few 10mm bolts.
- Install the New Module: Seat your replacement PCM into the bracket and secure it. Reconnect the electrical harnesses, ensuring they click firmly into place.
- Reconnect the Battery: Attach the negative battery terminal. The vehicle may require a security relearn procedure, which typically involves turning the key to the ‘ON’ position for 10-15 minutes. Consult your owner’s manual for specific steps.
Verified Vehicle Compatibility
This module is a direct fit for a wide range of GM trucks and vans. Please verify your vehicle is on this list and that your original module carries the ID 9355699 or one of the interchangeable part numbers listed below. Matching this ID is critical for compatibility.
Interchangeable Part Numbers: 09355699, 16266645, 16250279, 16258815, 09366810, 9366810
- Chevrolet/GMC Trucks (1998-1999): C/K 1500, 2500, 3500 (Gasoline)
- Chevrolet/GMC Vans (1998-1999): Express / Savana 1500, 2500, 3500 (Gasoline)
- Chevrolet/GMC SUVs (1998-1999): Suburban, Tahoe, Yukon (Gasoline)
- Cadillac (1999): Escalade
- Chevrolet/GMC S-Series (1998): S10, S15, Sonoma, Blazer, Jimmy (4.3L V6)
- Oldsmobile (1998): Bravada (4.3L V6)
- GMC (1998): Envoy (4.3L V6)
- Chevrolet/GMC Mini-Vans (1998): Astro / Safari
- Isuzu (1998): Hombre (4.3L V6)
Frequently Asked Questions
Do I need to do any programming or flashing myself?
No. We handle all the programming for you before shipment. We use your vehicle’s VIN to load the correct GM software and updates, so it arrives ready to install.
What is a VIN and where do I find it?
The VIN is your 17-digit Vehicle Identification Number. You can find it on your vehicle’s registration, insurance card, or on a small plate on the driver’s side of the dashboard, visible through the windshield.
Is this a new part?
This is a high-quality, tested, and inspected used part sourced from a salvaged vehicle. This allows us to provide a reliable and affordable solution compared to a new dealer part.
My original part number isn’t 9355699, but it’s on the interchange list. Will this work?
Yes. The part numbers 16266645, 16250279, 16258815, 09366810, and 9366810 are all interchangeable with 9355699. As long as your vehicle is on the fitment list, this module will function correctly once programmed to your VIN.
What happens after I place my order?
After you complete your purchase, you will need to send us your vehicle’s VIN. We cannot program and ship the module without it. Once we receive your VIN, we will program the PCM and typically ship it within one business day.