If your 1998-1999 GMC Savana 3500 is acting up—stalling, running rough, or throwing a stubborn Check Engine Light—the Powertrain Control Module (PCM) is often the culprit. As a technician with over two decades of experience, I’ve seen how a failing engine computer can cause a host of frustrating, hard-to-diagnose problems. This isn’t just a part; it’s the brain of your vehicle’s engine and transmission, and when it falters, your work van is dead in the water.
This is your direct, no-hassle solution. We’re offering a reliable, tested OEM PCM that replaces part number 16258815 and many others. The biggest advantage? We flash it with the latest GM software updates specifically for your van’s VIN before it ships. This means you get a component that’s ready for installation right out of the box, saving you a costly trip to the dealership for programming. It’s the smart, efficient fix for both professional mechanics and dedicated DIYers.
Is Your GM Truck or Van Showing These Symptoms?
A failing PCM can manifest in many ways. If you’re experiencing any of the following, a replacement engine computer could be the solution you need:
- âś” Persistent Check Engine Light (CEL)
- âś” Diagnostic Trouble Codes (DTCs) like P0601, P0605, or P0606 (Internal Module Failure)
- âś” Vehicle won’t start or has intermittent starting issues
- âś” Rough or unstable idle
- âś” Poor fuel economy
- âś” Hesitation or stumbling during acceleration
- âś” Failed emissions test
- âś” Erratic or harsh transmission shifting
From the Diagnostic Bay: The Ghost in the Machine
I remember a ’99 Express 3500 that came into my shop a few years back. The owner, a plumber, said it would randomly stall at traffic lights and sometimes wouldn’t restart for an hour. Two other shops had already replaced the fuel pump and ignition coil to no avail. After hooking up my scan tool and monitoring live data, I noticed the 5-volt reference signal would occasionally drop out right before a stall—a classic sign of an internal PCM short. We swapped in a VIN-programmed PCM just like this one, performed the security relearn, and the van ran perfectly. The owner was back on the job the next day. It’s often not the big mechanical parts, but the electronics that create these phantom problems.
A Straightforward Guide to Installation
Installing your replacement 1998-1999 Savana 3500 PCM is a manageable job for a DIYer with basic tools. Follow these steps carefully to ensure a smooth process.
- Safety First: Disconnect the negative terminal from your vehicle’s battery and secure it away from the post to prevent accidental contact.
- Locate the PCM: On most 1998-1999 Savana and Express vans, the PCM is located in the engine compartment, typically on the driver’s side, mounted near the firewall or inner fender.
- Disconnect the Connectors: The PCM will have several large multi-pin connectors. Each has a locking tab or lever. Carefully release the locks and gently pull the connectors straight out. Never force them.
- Remove the Old Module: Unbolt the PCM from its mounting bracket. Keep the hardware, as you may need to reuse it.
- Install the New Module: Mount your new, pre-programmed PCM onto the bracket and secure it with the bolts.
- Reconnect Everything: Firmly press the electrical connectors into the new PCM until they click into place. Re-engage the locking levers. Reconnect the negative battery terminal.
- Perform Security Relearn (CRITICAL): Your vehicle’s anti-theft system (Passlock/VATS) needs to sync with the new PCM. The standard procedure is: Turn the key to ‘ON’ (don’t start) for 10-15 minutes until the ‘Security’ light turns off or stops flashing. Turn the key ‘OFF’ for 10 seconds. Repeat this cycle two more times (for a total of 3 cycles). The vehicle should then start and run.
Verified Vehicle Compatibility
This PCM, identified by service ID 9355699, is a direct replacement for multiple part numbers and fits a wide range of GM vehicles. Please confirm your vehicle is on this list. It is compatible with part numbers: 09355699, 16266645, 9355699, 16250279, 16258815, 09366810, 9366810.
Fits Models Including:
- ASTRO & SAFARI (1998)
- BLAZER S10 & JIMMY S15 (1998)
- BRAVADA (1998)
- CHEVROLET & GMC PICKUPS 1500/2500/3500 (1998-1999)
- ESCALADE (1999)
- ENVOY (1998)
- EXPRESS & SAVANA VANS 1500/2500/3500 (1998-1999)
- ISUZU HOMBRE (1998, 4.3L)
- S10/S15/SONOMA (1998, 4.3L)
- SUBURBAN 1500/2500 (1998-1999)
- TAHOE & YUKON (1998-1999)
Note: This is a partial list. Compatibility depends on specific options. Providing your VIN is essential for correct programming.
Frequently Asked Questions
What does ‘VIN Programmed’ mean for me?
It means we load the specific software from GM for your exact vehicle using its Vehicle Identification Number (VIN). This ensures all systems, from the engine timing to the transmission shift points, operate exactly as the factory intended. It eliminates the need for expensive dealer programming.
Do I need to do anything after I install it?
Yes. After installing the module, you must perform the vehicle’s security relearn procedure. This syncs the new PCM to your vehicle’s anti-theft system. It’s a simple process that takes about 30 minutes and requires only your ignition key (see installation guide above).
Is this a new part?
No, this is a thoroughly tested, genuine OEM part sourced from a salvaged vehicle. We find these OEM units are often more reliable than aftermarket alternatives. It’s a dependable and cost-effective repair solution.
Why is my original part number different but still compatible?
Automakers like GM frequently update and consolidate part numbers over time. A newer part number often supersedes several older ones. This module, which interchanges with ID 9355699, is the correct service replacement for all the part numbers listed, ensuring proper function.
Where is the PCM located on my 1999 Savana 3500?
On the 1998-1999 Savana and Express vans, the PCM (or ECM) is typically found in the engine compartment, mounted to the driver’s side inner fender or near the firewall.