Is Your Late 90s GM Truck or Van Running Rough?
If you’re dealing with frustrating issues like a persistent Check Engine Light, poor fuel economy, erratic shifting, or even a no-start condition in your 1998 or 1999 GM vehicle, a failing Powertrain Control Module (PCM) is a very likely culprit. This central computer is the brain of your vehicle’s engine and transmission, and when it starts to fail, it can cause a cascade of problems that are difficult to diagnose. Don’t let a faulty computer keep your reliable truck off the road. This genuine, used OEM PCM, part number 9355699, is the definitive solution to restore your vehicle’s performance and reliability.
From the Diagnostic Bay
We had a 1999 GMC Yukon come into the shop that was driving the owner crazy. It would randomly stall at stoplights and had a harsh 1-2 shift. The owner had already replaced the fuel pump and throttle position sensor with no luck. After hooking up our scanner, we noticed erratic data streams from the PCM and a few communication error codes. Instead of chasing more sensors, we identified the PCM as the root cause. A common mistake is to throw parts at these symptoms. Verifying power and grounds to the PCM is a critical first step, but often, the internal circuitry of these 20+ year-old modules simply wears out. Replacing the PCM with a properly programmed unit like this one brought the Yukon back to life instantly.
Diagnosing a Faulty 1998-1999 Chevrolet 1500 PCM
The PCM, also known as the ECM or ECU, is responsible for managing everything from fuel injection and ignition timing to transmission shift points and emissions controls. Due to age, heat cycles, and vibrations, the internal components can degrade over time. This particular 1998-1999 Chevrolet 1500 PCM is a common failure point across a wide range of GM trucks and vans. If you’re experiencing any of the following, it’s time to consider a replacement.
Common Symptoms of PCM Failure
- ✔ Check Engine Light: The light is on with communication-related codes (U-codes) or multiple, seemingly unrelated sensor codes.
- ✔ No-Start or Hard-Start: The engine cranks but won’t start, or takes an extended time to fire up, especially when warm.
- ✔ Poor Engine Performance: Noticeable loss of power, hesitation during acceleration, stumbling, or random misfires.
- ✔ Reduced Fuel Economy: A sudden and unexplained drop in your vehicle’s MPG is a strong indicator of an engine management problem.
- ✔ Erratic Transmission Shifting: The transmission may shift harshly, slip between gears, or get stuck in one gear (limp mode).
- ✔ Failed Emissions Test: Inability to pass smog or emissions testing due to PCM-related fault codes.
The Simple, Reliable Solution: VIN-Programmed Replacement
This isn’t just a used part pulled from a yard. We take genuine OEM units and flash them with the latest official GM software updates specifically for your vehicle. By providing us with your Vehicle Identification Number (VIN) at checkout, you receive a module that is ready for installation. This process ensures compatibility and optimal performance, correcting many of the software-related issues that may have developed over the years.
Key Benefits:
- VIN-Programmed: We load the correct software for your specific vehicle, ensuring a seamless integration.
- OEM Quality: A genuine used GM part offers superior reliability compared to many aftermarket alternatives.
- Cost-Effective: Get your truck back on the road for a fraction of the cost of a new module from a dealership.
- Plug-and-Play Potential: In many cases, after installation, you will only need to perform a simple security relearn procedure, which can be done without a scan tool.
This module is a direct replacement for part numbers 09355699, 16266645, 9355699, 16250279, 16258815, 09366810, and 9366810. Please verify your part number before ordering to ensure a perfect match. The module is typically located in the engine bay, often on the driver’s side inner fender.
Frequently Asked Questions
Do I need to program this module?
No. We handle the programming for you before we ship it. Simply provide your vehicle’s VIN when you place your order, and we will flash the module with the latest GM calibration for your exact vehicle.
Is this a new part?
No, this is a high-quality, tested, genuine OEM part sourced from a salvaged vehicle. This ensures original factory fitment and reliability at a great price.
Will I need to do anything after installation?
After installing the PCM, you will likely need to perform a security relearn procedure (also known as the Passlock or VATS relearn). This procedure syncs the new PCM with your vehicle’s anti-theft system and typically involves a sequence of key turns. Instructions are readily available online for your specific model. In some cases, a Crankshaft Variation Relearn (CASE relearn) may be needed with a scan tool to clear a P1336 code, but this often does not affect vehicle operation.
Where is the PCM located on my truck?
On most 1998-1999 GM full-size trucks and SUVs (like the Silverado, Sierra, Tahoe, Suburban), the PCM is located in the engine compartment on the driver’s side, near the firewall or on the inner fender. On vans (Express, Savana), it’s often on the left rear side of the engine compartment.
How do I provide my VIN?
You can add your 17-digit VIN to the notes section during checkout or send it to us in a message after you complete your purchase. We cannot ship your order until we receive the VIN.