Is Your 2005 Equinox or GM Vehicle Running Rough?
A failing Powertrain Control Module (PCM), also known as an Engine Control Module (ECM), is a common but often misdiagnosed issue in vehicles like the 2005 Chevrolet Equinox. When this critical component begins to fail, it can cause a cascade of frustrating and seemingly unrelated problems, from a simple check engine light to a vehicle that refuses to start. You need a reliable solution that doesn’t involve expensive dealership guesswork. This genuine, used OEM Powertrain Control Module, part number 12591279, is the answer. It arrives at your door pre-programmed with the latest GM software updates, specifically matched to your vehicle’s VIN, ensuring a straightforward installation and restoring your vehicle’s performance.
From the Diagnostic Bay
We had a 2005 Saturn Relay come into the shop with a bizarre, intermittent stalling problem. The owner had already replaced the fuel pump and crankshaft position sensor, but the issue persisted. The engine would run perfectly for days, then suddenly die at a stoplight. No codes were being stored consistently. After hours of chasing wires and checking grounds, we hooked up a scope to the PCM’s main power and communication lines. We discovered that the 5-volt reference signal inside the module would momentarily drop out, causing the shutdown. We installed one of these VIN-programmed modules, performed the security relearn, and the Relay has been running flawlessly ever since. It’s a classic case where the central brain was the culprit all along.
Common Symptoms of a Failing Engine Computer
- ✔ Persistent Check Engine Light (CEL) that won’t clear or returns with various codes.
- ✔ Engine stalling, stumbling, or hesitating, especially under load.
- ✔ A complete no-start condition where the engine cranks but won’t fire up.
- ✔ Poor fuel economy and a noticeable decrease in engine power.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ Communication errors with diagnostic scan tools.
- ✔ Intermittent issues with cooling fans, A/C, or other electronically controlled systems.
Why Our Pre-Programmed 2005 Equinox Engine Computer is the Smart Choice
Replacing the PCM in these GM vehicles isn’t as simple as swapping the part. The module is tied to your vehicle’s security system (Passlock/Passkey) and contains specific operational data for your engine and transmission. Our service eliminates the hassle and extra cost of dealership programming. We take your Vehicle Identification Number (VIN) at the time of purchase and flash the module with the exact software your vehicle needs. This ensures all components communicate correctly and the engine operates according to factory specifications.
This is a genuine, used OEM part sourced from a salvaged vehicle, offering the same reliability and performance as the original unit at a fraction of the cost of a new module. Each unit is carefully inspected and tested before being programmed and shipped.
Installation and Relearn Procedure
Physical installation is straightforward: disconnect the battery, unplug the electrical connectors from the old PCM, unbolt it from its mounting location (typically the left-hand side of the engine compartment), and install the new one. After installation, you will likely need to perform a simple security relearn procedure. This can usually be done without special tools and involves a sequence of turning the key in the ignition. In some cases, a Crankshaft Variation Relearn (CASE Relearn) may be required, which needs a capable scan tool. This procedure synchronizes the PCM with the crankshaft position sensor for optimal ignition timing and misfire detection.
Guaranteed Fitment
This module is a direct replacement for part numbers 12591279 and 12591856. It is guaranteed to fit the following vehicles:
- 2005 Chevrolet Equinox (Electronic Control Module; LH engine compartment)
- 2005 Chevrolet Malibu (Electronic Control Module; LH dash, VIN Z 4th digit, New Style, 3.5L)
- 2005 Chevrolet Uplander (Electronic Control Module; LH engine compartment)
- 2005 Pontiac G6 (Electronic Control Module; Sdn, LH front engine compartment)
- 2005 Pontiac Montana (Electronic Control Module; LH engine compartment, SV6)
- 2005-2006 Saturn Relay (Electronic Control Module; LH engine compartment, 3.5L for 06)
- 2005 Buick Terraza (Electronic Control Module; LH engine compartment)
Frequently Asked Questions
Do I need to do any programming after I install this computer?
No programming is required. We flash the computer with your vehicle’s VIN-specific software before shipping. However, you will need to perform a security relearn procedure, which can typically be done at home in about 30 minutes without special tools. A CASE relearn may also be needed for optimal performance, which requires a scan tool.
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, factory-spec part at a significant savings compared to a new unit from a dealer.
How do I provide you with my VIN?
After you complete your purchase, you can add your VIN to the order notes or send it to us via email. We will contact you if we do not receive it promptly. We cannot ship the module until we have your VIN to program it correctly.
Will this computer fix my vehicle’s problem?
This part will resolve any issues directly caused by a faulty PCM. However, it is crucial that your vehicle has been properly diagnosed. This part will not fix problems related to other faulty components like sensors, wiring, or mechanical issues.
What is the difference between a PCM and an ECM?
The terms are often used interchangeably. ECM (Engine Control Module) typically controls only engine functions. PCM (Powertrain Control Module) controls both the engine and the transmission. For this specific vehicle and part, it functions as the PCM.