Is Your GM Truck or Van Running Rough?
If your 1998-1999 Chevrolet Express, GMC Savana, or another compatible GM vehicle is suffering from perplexing issues like a persistent check engine light, stalling, poor fuel economy, or erratic shifting, the problem may lie with its electronic brain: the Powertrain Control Module (PCM). This central computer is responsible for managing everything from fuel injection and ignition timing to transmission shift points. When it fails, it can cause a cascade of problems that are often misdiagnosed, leading to wasted time and money on unnecessary parts.
From the Diagnostic Bay
I once had a 1999 Suburban in the shop with a classic no-start condition. The owner had already replaced the fuel pump, crank sensor, and ignition coil based on advice from forums. The vehicle still wouldn’t fire up. After hooking up our professional scan tool, we found no communication with the PCM. A quick check of the power and ground circuits to the module confirmed they were good. The PCM itself had failed internally. We installed a VIN-programmed unit just like this one, performed the security relearn, and the truck started on the first crank. It’s a powerful reminder that starting with the central controller can save a lot of diagnostic headaches.
Symptoms of a Failing PCM
- ✔ Persistent Check Engine Light (CEL) with various trouble codes.
- ✔ Engine stalling, stumbling, or hesitating during acceleration.
- ✔ No-start or hard-starting conditions, especially when warm.
- ✔ Noticeable decrease in fuel efficiency.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ Failure to pass state emissions testing.
- ✔ Communication errors with diagnostic scan tools.
The Direct Solution: A VIN-Programmed 1998-1999 Express PCM
Don’t settle for a generic, unprogrammed module that requires an expensive trip to the dealership. This is a genuine, used OEM PCM, part number 16266645, meticulously tested and sourced from a salvaged vehicle. The critical difference is our professional programming service. Before we ship it, we flash the module with the latest official GM software updates and program it specifically to your vehicle’s Vehicle Identification Number (VIN). This ensures that the computer has the correct calibration for your engine, transmission, and options, making for a seamless installation process.
This module is a direct replacement for a wide range of GM trucks and vans from this era, including the Chevrolet Silverado, GMC Sierra, Tahoe, Yukon, Suburban, and more. It is a reliable and cost-effective solution to get your vehicle back to factory-spec performance without the high cost of a new part from the dealer.
Installation and Setup
Physically installing the PCM is typically straightforward, involving disconnecting the battery and swapping the module. After installation, some vehicles may require a security relearn procedure (often called Passlock or VATS relearn) or a Crankshaft Position Sensor (CASE) relearn. These procedures can often be performed without special tools and instructions are widely available online, or can be completed by any competent local mechanic.
Frequently Asked Questions
Do I need to take this part to a dealer for programming?
No. We handle the programming for you before shipment. Simply provide us with your vehicle’s 17-digit VIN during or after checkout, and the module will arrive ready to be installed.
Is this a new computer?
No, this is a high-quality, tested used OEM part sourced from a salvaged vehicle. This provides the reliability of a genuine GM part at a fraction of the cost of a new one.
What is a CASE relearn and will I need to perform one?
A CASE (Crankshaft Angle Sensor Error) relearn synchronizes the new PCM with your engine’s crankshaft position sensor. It is sometimes required to clear specific trouble codes after a PCM replacement. This procedure can be done with a capable scan tool by a local shop, or sometimes by the owner following a specific drive cycle.
Where can I find my VIN?
Your VIN can be found on a metal plate on the driver’s side of the dashboard (visible through the windshield), on the driver’s side door jamb sticker, or on your vehicle’s registration and insurance documents.
Could a bad PCM cause my transmission to shift incorrectly?
Absolutely. The PCM controls both engine and transmission functions. A failing module can cause a variety of shifting problems, including delayed shifts, harsh engagement, or being stuck in one gear (limp mode).