Is Your 1999-2000 GMC Sierra 1500 Running Rough or Not at All?
If you’re dealing with baffling electrical gremlins in your GMC Sierra or another compatible GM truck, the Powertrain Control Module (PCM) is often the culprit. As a mechanic with over two decades of diagnostic experience, I’ve seen these exact issues countless times. A truck comes into the bay with a check engine light that won’t go away, it shifts hard between gears, gets terrible gas mileage, or sometimes just refuses to start. The owner has often replaced multiple sensors, but the problem persists. That’s because the ‘brain’ of the truck is malfunctioning.
Common Symptoms of a Failing GM PCM
The PCM, or ECM as it’s also known, is the central computer for your engine and transmission. When it starts to fail, the symptoms can be all over the place. Look out for:
- โ Check Engine Light with communication error codes (U-codes) or random sensor codes.
- โ Harsh or erratic automatic transmission shifting.
- โ Engine cranks but won’t start (no-start condition).
- โ A noticeable drop in fuel economy.
- โ Stalling, stumbling, or misfiring for no apparent reason.
- โ Failure to pass an emissions test.
Expert Pro Tip: Check Your Grounds First!
Before you condemn your PCM, grab a multimeter. On these GM trucks, a corroded or loose ground wire can mimic a bad module. Check the main ground straps from the engine block to the chassis and the battery negative cable connection points. Also, check for consistent battery voltage and a clean ground signal at the PCM’s electrical connectors. In my shop, I’ve found that about 10% of suspected PCM failures were actually just a bad ground, saving the customer hundreds of dollars. A solid diagnostic process is key.
The Right Fix: A Reliable, Programmed Replacement
Replacing the PCM isn’t just about swapping boxes. The module must be programmed with the correct software for your truck’s specific Vehicle Identification Number (VIN). Without this step, the vehicle won’t run correctly, or at all. Dealerships charge a premium for this service. We take care of that for you.
This replacement PCM is the solution to get your truck running right again. We handle the complex part, so you don’t have to.
Why Choose Our Pre-Programmed Module?
- โ VIN-Specific Programming: We flash the module with the latest GM-authorized software for your exact truck. This ensures all systems, from the engine to the anti-theft system, communicate correctly.
- โ No Dealer Visit Required: Your module arrives ready for installation. Once installed, you will need to perform a simple security relearn procedure (which takes about 30 minutes and requires only your key), but you avoid a costly trip to the dealership for programming.
- โ Solves Known Issues: The updated software we install often corrects factory bugs and improves shifting patterns and fuel management beyond what your original module could do.
Guaranteed Compatibility
This module is a direct replacement for a wide range of GM trucks and vans. To ensure a perfect match, please verify that your original part number is on this list:
- โ Part Numbers: 16263494, 16265035, 8162634940, 218-11787, 21811787
Simple Installation Process
For a 1999-2000 GMC Sierra 1500 with the 6-cylinder engine, the PCM is typically located under the battery on the driver’s side. The process is straightforward for a DIY mechanic.
- Disconnect the Battery: Always disconnect the negative battery terminal first.
- Locate and Remove the Old PCM: Remove the battery and battery tray to access the module. Carefully unplug the electrical connectors and unbolt the module from its bracket.
- Install the New PCM: Bolt the new module in place and securely reconnect the electrical harnesses. Ensure the connectors click into place. Reinstall the battery tray and battery.
- Perform Security Relearn: Reconnect the battery. You will now need to perform the vehicle’s security relearn procedure. This typically involves turning the key to the ‘ON’ position for 10-15 minutes, then ‘OFF’, and repeating this cycle three times. Your vehicle’s manual will have the specific instructions.
By providing your VIN at checkout, you ensure we send you a module that is perfectly matched and ready to restore your truck’s performance and reliability. Get your Sierra back on the road with confidence.