Is Your Saturn Sky Running Rough?
If you’re dealing with a persistent Check Engine Light, erratic engine behavior, stalling, or a no-start condition, a failing Powertrain Control Module (PCM) is a likely culprit. The PCM is the brain of your vehicle, managing everything from fuel injection and ignition timing to transmission shifting. When it fails, it can cause a cascade of frustrating and difficult-to-diagnose problems. This replacement PCM, service number 12635901, is the definitive solution to restore your vehicle’s performance and reliability.
From the Diagnostic Bay
We had a 2009 Saturn Sky 2.4L come into the shop that was driving its owner crazy. It would start fine cold, but after 15 minutes of driving, it would intermittently stall at stoplights and throw a U0100 ‘Lost Communication with ECM/PCM’ code. We checked all the wiring, grounds, and connectors—they were perfect. The issue was internal to the PCM; heat was causing a component on the circuit board to fail. Instead of a costly and time-consuming diagnostic rabbit hole, we installed a VIN-programmed module just like this one. After a quick security relearn, the car ran perfectly, the code was gone, and the customer was back on the road in no time. A pre-programmed module is the most efficient way to solve these phantom electronic issues.
Why Choose Our Programmed Saturn Sky PCM?
This isn’t just a replacement part; it’s a complete, ready-to-install solution. We take the guesswork and extra expense out of the repair process. When you order from us, we use the Vehicle Identification Number (VIN) you provide to flash the module with the latest, most stable software updates directly from GM. This ensures perfect compatibility and can even resolve factory-known drivability issues you might not have known were software-related. This module is a direct replacement for multiple service numbers, including 12597125, 12612397, 12629019, and more, making it a versatile fix for a wide range of GM vehicles.
Symptoms of a Failing GM PCM
- ✔ Persistent Check Engine Light (CEL) that won’t clear.
- ✔ Error codes related to module communication (U-codes).
- ✔ Engine stalling, stumbling, or misfiring for no apparent reason.
- ✔ Drastic decrease in fuel economy.
- ✔ Harsh or incorrect automatic transmission shifting.
- ✔ The vehicle cranks but refuses to start.
- ✔ Failure to pass state emissions testing.
Installation is Straightforward
Once you receive your pre-programmed module, the physical installation is as simple as disconnecting the battery, unplugging the electrical connectors from the old PCM, unbolting it, and installing the new one in its place. After installation, you will likely need to perform a simple security relearn procedure, often called a ‘key-cycle relearn’. This procedure pairs the new PCM to your vehicle’s anti-theft system and typically involves turning the key to the ‘ON’ position for 10-15 minutes, then off, and repeating two more times. This can be done in your own driveway without any special tools, saving you a trip to the dealership.
Frequently Asked Questions
Do I need to have this computer programmed?
No. This module comes fully programmed to your vehicle’s specific VIN before we ship it. It is ready for installation right out of the box.
What is a VIN and where do I find it?
The VIN is your vehicle’s unique 17-digit identification number. You can find it on the driver’s side of the dashboard (visible through the windshield), on the driver’s side door jamb sticker, or on your vehicle’s registration and insurance documents.
Is any other setup required after I install it?
In most cases, you will need to perform a security relearn procedure, which can be done without special tools. Instructions are readily available online for your specific model. In some cases, a Crankshaft Variation (CASE) relearn may be needed, which requires a capable scan tool.
How can I be sure my PCM is the actual problem?
While the symptoms listed are strong indicators, it’s always best to have a proper diagnosis performed. This includes checking all power and ground connections to the PCM and ruling out wiring or sensor issues before replacing the module.
This part number is different than mine. Will it work?
Yes. This module, 12635901, is the hardware that supersedes and replaces a range of earlier service numbers like 12597125, 12612397, and others listed in the description. As long as your vehicle is on the compatibility list, we will program it to function identically to your original.