Restore Peak Performance to Your GM Vehicle
Is your 2005 Buick Terraza, Chevy Equinox, or Pontiac G6 suffering from erratic engine behavior, poor fuel economy, or a persistent Check Engine Light? These are classic signs of a failing Powertrain Control Module (PCM), the electronic brain of your vehicle. A faulty PCM can lead to a cascade of frustrating issues, from stalling and rough idling to transmission shifting problems and even a no-start condition. Don’t let a malfunctioning computer keep you off the road. This genuine, used OEM PCM, part number 12591279, is the reliable and cost-effective solution you need to get your vehicle running smoothly again.
From the Diagnostic Bay
We had a 2005 Saturn Relay come into the shop with a complaint of intermittent stalling at stoplights and a random P0300 multiple misfire code that previous shops couldn’t solve. They had already replaced the plugs, wires, and ignition coil pack. After hooking up our diagnostic scanner and monitoring live data, we noticed the injector pulse width for cylinder 3 was behaving erratically just before a stall event. A quick check with a noid light confirmed the injector signal was dropping out. Instead of a bad injector, we traced the wiring back to the PCM and found the driver circuit for that injector was failing internally. We sourced a quality used module just like this one, programmed it to the van’s VIN, and the problem was solved permanently. It’s a reminder that sometimes the root cause lies within the controller itself.
Is Your Vehicle Showing Signs of PCM Failure?
A failing engine computer can manifest in numerous ways. If you’re experiencing any of the following symptoms, a faulty PCM could be the culprit:
- ✔ Check Engine Light: The light is on, and you may have codes related to sensor circuits, injector drivers, or internal module faults.
- ✔ Engine Stalling or Misfiring: The engine may stall unexpectedly, run rough, or misfire without a clear mechanical cause.
- ✔ Poor Performance & Fuel Economy: A noticeable drop in power, acceleration, and miles per gallon is a common symptom.
- ✔ Harsh or Incorrect Shifting: The PCM also controls transmission functions, and a fault can lead to hard shifts or getting stuck in gear.
- ✔ No-Start Condition: In severe cases, the PCM can fail completely, preventing the engine from starting by not firing the ignition coils or fuel injectors.
- ✔ Communication Issues: Your diagnostic scan tool may be unable to communicate with the engine control module.
The Critical Importance of VIN Programming
Simply swapping a used PCM from another vehicle will not work. Modern vehicles use sophisticated anti-theft systems and require specific software calibrations for the engine, transmission, and all equipped options. That’s why our service is essential. When you purchase this module, you provide us with your vehicle’s 17-digit Vehicle Identification Number (VIN). Our technicians will then use professional equipment to flash the module with the latest, most up-to-date software directly from GM for your exact vehicle. This process ensures:
- Correct Engine & Transmission Calibration: Your vehicle operates exactly as the manufacturer intended.
- Proper Anti-Theft System Integration: The module is synced to your vehicle, preventing a no-start security lockout.
- Plug-and-Play Installation: In most cases, this eliminates the need for an expensive trip to the dealership for further programming.
Installing Your 2005 Terraza PCM
Installation is a straightforward process for a DIY mechanic or any professional technician. The module is typically located in the left-hand (driver’s side) engine compartment or under the dash, depending on your specific model. The general steps involve disconnecting the vehicle’s battery, carefully unplugging the electrical connectors from the old module, unbolting it from its bracket, and then installing the new one in the reverse order. After reconnecting the battery, the vehicle is ready to start. While our programming handles the majority of the setup, some vehicles may require a simple security relearn procedure, which can often be done without special tools.
Direct Replacement for Part Numbers:
- 12591279
- 12591856
Guaranteed Fitment For:
- 2005 Chevrolet Equinox – Electronic Control Module; (LH engine compartment)
- 2005 Saturn Relay – Electronic Control Module; (LH engine compartment)
- 2006 Saturn Relay – Electronic Control Module; (LH engine compartment), 3.5L
- 2005 Chevrolet Malibu – Electronic Control Module; (LH dash), VIN Z (4th digit, New Style), 3.5L
- 2005 Buick Montana – Electronic Control Module; (LH engine compartment), SV6
- 2005 Buick Terraza – Electronic Control Module; (LH engine compartment)
- 2005 Pontiac G6 – Electronic Control Module; (Sdn), (LH front engine compartment)
- 2005 Chevrolet Uplander – Electronic Control Module; (LH engine compartment)
This is a high-quality, tested, and properly programmed 2005 Terraza PCM that offers a reliable and affordable alternative to expensive dealership parts. Restore your vehicle’s health and drive with confidence. Order today and provide your VIN to get the process started.
Frequently Asked Questions
Do I need to send my old computer (core) back?
No, a core return is not required for this part. This is an outright purchase of a used, programmed module.
Is any additional programming needed after installation?
Because we program the module to your specific VIN before shipping, no further programming is typically required. In some rare cases, a security or crankshaft position sensor relearn may be necessary, which can be performed by most automotive shops or with certain high-end scan tools.
Where do I find my VIN?
Your 17-digit Vehicle Identification Number (VIN) can be found on your vehicle’s registration, insurance card, or on a metal plate on the driver’s side of the dashboard, visible through the windshield.
What if I have a different part number?
This module is a direct replacement for part numbers 12591279 and 12591856. Please verify that your original module has one of these numbers to ensure compatibility. If you are unsure, please contact us with your VIN before ordering.
Is this a new part?
No, this is a genuine OEM part that has been sourced from a salvaged vehicle. Each unit is inspected and tested to ensure it is fully functional before being programmed and shipped.