Restore Your Truck’s Performance and Reliability
If your 1999-2000 GMC 3500 Pickup is suffering from baffling issues like stalling, erratic shifting, a persistent check engine light, or a no-start condition, the problem often lies with a failing Powertrain Control Module (PCM). As the central computer of your vehicle, the PCM governs everything from fuel mixture and ignition timing to transmission operation. When it fails, your truck’s performance and reliability suffer. This isn’t just an inconvenience; it can leave you stranded.
As a technician with over 20 years of experience, I’ve seen firsthand how a faulty PCM can cause mechanics and owners to chase their tails, replacing perfectly good sensors. This replacement 1999-2000 GMC 3500 PCM is the definitive solution. We take the guesswork out of the repair by pre-programming the module to your truck’s exact Vehicle Identification Number (VIN) before it ships. This ensures it has the latest GM software updates for optimal engine performance, fuel economy, and smooth transmission function. Simply provide your VIN at checkout, and we’ll handle the complex programming for you.
Case Study: A Tricky Diagnosis
I remember a 2000 Chevy 2500—which uses this same PCM platform—that came into my shop with a frustrating, intermittent no-start problem. The owner had already replaced the battery, starter, and crank sensor. We could find no rhyme or reason to it. After hours of diagnostic work, we hooked up a scope and monitored the PCM’s internal voltage. We discovered the processor was intermittently dropping out under certain temperature conditions. A new, properly programmed PCM fixed the issue instantly. The customer was thrilled to have his reliable workhorse back. This highlights how a failing computer can mimic other mechanical or electrical failures.
Is Your Truck Exhibiting These Issues?
A failing PCM can manifest in numerous ways. If you’re experiencing any of the following, it’s a strong indicator that your engine computer needs replacement:
- ✔ Check Engine Light is on with codes like P0601 (Internal Control Module Memory Check Sum Error) or P0606 (ECM/PCM Processor Fault).
- ✔ The engine cranks but refuses to start.
- ✔ Unexplained drops in fuel economy.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ The vehicle stalls for no apparent reason, either while driving or at idle.
- ✔ Failure to pass state emissions testing.
- ✔ Communication errors with diagnostic scan tools.
A Straightforward Guide to Installation
Installing your new 1999-2000 GMC 3500 PCM is a manageable job for a confident DIYer. Follow these steps carefully for a successful replacement.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery and secure it away from the post to prevent any accidental reconnection.
- Locate the PCM: On most 1999-2000 GM trucks, the PCM is located in the engine compartment on the driver’s side, often near the fender or firewall.
- Disconnect the Connectors: Carefully unclip and remove the electrical wiring harness connectors from the old PCM. These connectors have locking tabs that need to be released. Avoid pulling on the wires themselves.
- Remove the Old Module: Unbolt the old PCM from its mounting bracket. There are typically two or three bolts holding it in place.
- Install the New Module: Mount your new, pre-programmed PCM onto the bracket and secure it with the original bolts.
- Reconnect Everything: Firmly plug the wiring harness connectors into the new module until they click into place. Reconnect the negative battery terminal.
- Perform Security Relearn (If Necessary): In some cases, you may need to perform a security or anti-theft relearn procedure. This typically involves turning the key to the ‘ON’ position for 10-15 minutes, then off, and repeating two more times before starting the engine. Consult your vehicle’s service information for the exact procedure.
Verified Vehicle Compatibility
This module is a direct replacement for part numbers 16263494, 16265035, and 8162634940. It is guaranteed to fit a wide range of GM trucks and vans. Please verify your vehicle is on the list below. The specific ID number (e.g., ID 16263494) is critical for certain models.
GMC: 1500/2500/3500 Pickups (99-00), Sierra 1500 (99-00), Sonoma (98-00), Jimmy (98-00), Yukon/Denali (99-00), Safari Van (99-01), Savana Van (99-02)
Cadillac: Escalade (99-00)
Oldsmobile: Bravada (98-00)
Isuzu: Hombre (98-00)
GMC Envoy: (98-00)
Note: This is a partial list. Please refer to the detailed fitment data provided in the original listing to confirm compatibility with your specific engine and options. A correct match is essential for your 1999-2000 GMC 3500 PCM to function correctly.
Frequently Asked Questions
What is a PCM and what does it do?
The Powertrain Control Module (PCM) is your vehicle’s main computer. It controls the engine and transmission functions, managing fuel injection, spark timing, emissions systems, and shift points to ensure the vehicle runs efficiently and smoothly.
Why is providing my VIN so important?
Your Vehicle Identification Number (VIN) allows us to program the PCM with the correct factory software and calibrations specific to your truck’s engine, transmission, and options. This step is critical for proper function and avoids a costly trip to the dealership.
Is this part ready to install out of the box?
Yes, it arrives pre-programmed to your VIN. In most cases, it’s a direct installation, though some GM vehicles may require a simple security relearn procedure that you can do yourself in about 30 minutes with just the ignition key.
Will this fix my check engine light?
If the check engine light is caused by an internal PCM failure (like code P0601), this module will resolve the issue. However, you should always diagnose the codes first to ensure the fault isn’t with a sensor or other component.
Where is the PCM located on my 1999 GMC 3500?
On the 1999-2000 GMC 3500 gasoline models, the PCM is typically found in the engine compartment, mounted on the driver’s side inner fender, near the battery.
What is the difference between a PCM and an ECM?
ECM stands for Engine Control Module. PCM (Powertrain Control Module) is a more inclusive term for a computer that controls both the engine AND the automatic transmission. For these vehicles, the terms are often used interchangeably as this single unit does both jobs.