Get Your GM Truck or SUV Running Reliably Again
As a technician with over two decades of experience, I’ve seen firsthand the headaches a failing Powertrain Control Module (PCM) can cause. From a vehicle that won’t start to erratic shifting and a persistent Check Engine Light, a faulty PCM can bring your entire vehicle to a standstill. This isn’t just an inconvenience; it’s a critical failure. This tested, used engine computer is the straightforward, dependable solution you’ve been looking for. It’s a genuine OEM part, sourced from a salvaged vehicle, that offers a cost-effective fix without the high price tag of a dealership.
The real value here is our professional programming service. Before this module ships, we flash it with the latest official GM software updates, specifically matched to your vehicle’s VIN. This means it arrives ready for installation, eliminating the need for expensive programming or a trip to the dealer. You’re getting a part that’s not only compatible but also optimized for your specific vehicle’s configuration, restoring its original performance and efficiency.
From the Diagnostic Bay: The Intermittent No-Start Nightmare
I remember a 1999 Tahoe that came into the shop on a tow truck. The owner was frustrated because it would randomly refuse to start. He had already replaced the battery, starter, and fuel pump. We checked for spark and fuel pressure, and everything seemed fine. The confusing part was the lack of consistent diagnostic trouble codes. After hours of tracing wires, we finally hooked up a scope to the PCM’s main communication lines and saw the signal drop out intermittently. The internal processor was failing under certain temperature conditions. We installed a VIN-programmed PCM just like this one, and the truck fired up instantly. It’s a classic example of how a failing 1998 Envoy PCM or its equivalent can create phantom issues that are nearly impossible to trace without pinpointing the source.
Is Your Vehicle Showing These PCM Failure Signs?
A failing engine computer can manifest in numerous ways. If you’re experiencing any of the following, a faulty PCM could be the culprit. Keep an eye out for these common symptoms and diagnostic codes:
- ✔ Check Engine Light is on with communication-related codes (e.g., P0601, P0605, P0606).
- ✔ The engine cranks but will not start.
- ✔ Rough or inconsistent engine idling.
- ✔ Poor fuel economy for no apparent reason.
- ✔ The transmission is not shifting correctly or feels stuck in one gear.
- ✔ Stalling or hesitation during acceleration.
- ✔ Loss of power from the engine.
A Straightforward Guide to Installation
Installing your programmed 1998 Envoy PCM is a manageable job for a confident DIYer. Following these steps will help ensure a smooth process. Remember, your new module comes pre-programmed, so no special computer equipment is needed for the installation itself.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery before starting any electrical work.
- Locate the PCM: On most of these GM trucks and vans, the PCM is located in the engine compartment, often on the driver’s or passenger’s side fender well or near the battery.
- Disconnect the Connectors: Carefully unclip the wiring harness connectors from the old PCM. These connectors have locking tabs that may need to be gently pried or squeezed to release. Avoid pulling on the wires themselves.
- Remove the Old Module: Unbolt the old PCM from its mounting bracket. There are typically a few bolts holding it in place.
- Install the New Module: Mount your new, programmed PCM onto the bracket and secure it with the bolts.
- Reconnect Everything: Firmly plug the wiring harness connectors into the new module. You should hear or feel a click as they lock into place. Reconnect the negative battery terminal.
- Security Relearn Procedure: In many cases, you will need to perform a security relearn procedure to sync the new PCM with your vehicle’s anti-theft system. This typically involves turning the key to the ‘ON’ position for 10-15 minutes, then off, and repeating the cycle two more times. Please verify the specific procedure for your model.
Verified Fitment for These GM Models
This engine control module is a direct replacement for service number 09355699 and is compatible with a wide range of GM vehicles. Please verify your original part number or consult the list below. This unit is interchangeable with part numbers 16266645, 09355699, 16250279, 16258815, and 09366810.
CHEVROLET 2500 PICKUP 98-99 (Gasoline)
CHEVROLET 3500 PICKUP 98-99 (Gasoline)
GMC 1500 PICKUP 98-99 (Gasoline)
GMC 2500 PICKUP 98-99 (Gasoline)
GMC 3500 PICKUP 98-99 (Gasoline)
TAHOE/YUKON 98-99 (Gasoline)
SUBURBAN 1500/2500 98-99 (Gasoline)
ESCALADE 99
EXPRESS 1500/2500/3500 VAN 98-99 (Gasoline)
SAVANA 1500/2500/3500 VAN 98-99 (Gasoline)
ASTRO/SAFARI 98
BLAZER S10/JIMMY S15 98 (w/o build date opt ZN4)
S10/S15/SONOMA 98 (4.3L, w/o build date opt ZN4)
BRAVADA 98 (w/o build date opt ZN4)
ENVOY 98 (w/o build date opt ZN4)
ISUZU HOMBRE 98 (4.3L, w/o extended build date opt ZN4)
Frequently Asked Questions
Frequently Asked Questions
Do I need to do anything after installing this PCM?
Because this module is pre-programmed to your VIN, the main software is ready to go. However, you will likely need to perform a security relearn procedure (often called Passlock or VATS relearn) so the vehicle recognizes the new computer. This procedure is simple and does not require special tools.
Is this a new part?
No, this is a high-quality, tested used OEM part that has been sourced from a salvaged vehicle. This allows us to provide a reliable and affordable solution.
How do I provide my VIN?
After you complete your purchase, you will need to send us your 17-digit Vehicle Identification Number (VIN). We cannot program and ship the module without it.
What if my original part number isn’t 16266645?
This module is compatible with several part numbers, including 09355699, 16250279, 16258815, and 09366810. As long as your original module has one of these numbers, this part will work for your vehicle.
Will this fix my check engine light?
If the check engine light is on due to an internal failure of the PCM (like code P0601), then yes, this part will resolve the issue. However, if the light is on for another reason (e.g., a bad oxygen sensor), you will still need to fix that separate problem.