Is Your Cadillac STS Running Rough or Not Starting?
If your 2005-2007 Cadillac STS or 2005 CTS is experiencing perplexing issues like random stalling, a persistent Check Engine Light, poor fuel economy, or erratic shifting, the root cause is often a failing Powertrain Control Module (PCM). The PCM is the central computer of your vehicle, responsible for managing everything from fuel injection and spark timing to transmission shift points. When it begins to fail, it can create a cascade of problems that are frustrating and difficult to diagnose. Don’t let a faulty computer keep your luxury sedan off the road. This is your direct, reliable solution.
This listing is for a genuine GM PCM, part number 12585814 (also compatible with 12600940 and YHTZ), that comes fully programmed specifically for your vehicle. We take your vehicle’s unique Vehicle Identification Number (VIN) and flash the module with the latest, most stable software updates directly from General Motors. This critical step ensures perfect compatibility and functionality, eliminating the need for an expensive trip to the dealership for programming. It’s the most efficient way to restore your Cadillac’s performance and reliability.
From the Diagnostic Bay
I once had a 2006 STS 3.6L come into the shop with a ghost of a problem. The owner complained of intermittent stalling at stoplights, but it would always start right back up. There were no consistent trouble codes, just a few random communication errors that would come and go. We checked fuel pressure, scanned for vacuum leaks, and tested the main sensors—everything looked perfect. After two days of chasing our tails, we decided to monitor the PCM’s live data stream on a long test drive. We finally caught it: for a split second, the processor would drop all its outputs, killing the engine. It was a classic case of internal PCM failure caused by heat and age. Swapping in a VIN-programmed module like this one solved the problem instantly. Sometimes, the brain itself is the issue, not the parts it’s controlling.
Symptoms of a Failing 2005-2007 STS PCM
A failing PCM can manifest in numerous ways. If you’re noticing any of the following symptoms, it’s a strong indicator that your vehicle’s main computer may need replacement. Proper diagnosis is always recommended, but these are the most common signs:
- ✔ Check Engine Light: The light is on, and you may have codes related to module communication (U-codes), sensor circuits, or processor faults (P06xx codes).
- ✔ Engine Stalling: The engine may stall for no apparent reason, either while driving or at an idle.
- ✔ No-Start Condition: The engine cranks but refuses to start, despite having fuel and spark.
- ✔ Poor Engine Performance: Noticeable loss of power, hesitation during acceleration, and rough idling.
- ✔ Reduced Fuel Economy: A sudden and unexplained drop in your vehicle’s MPG.
- ✔ Erratic Transmission Shifting: The transmission may shift harshly, late, or get stuck in one gear (limp mode).
- ✔ Communication Issues: Your diagnostic scan tool may be unable to communicate with the PCM.
The Plug-and-Programmed Solution
The biggest hurdle when replacing a modern vehicle’s computer is the programming. This isn’t a simple bolt-on part; it needs to be loaded with the correct software and security information for your specific car. Our service eliminates that obstacle. By providing your VIN at checkout, you receive a module that is ready for installation. We handle the complex part, so you can get back on the road faster.
Key Benefits:
- VIN-Specific Programming: Flashed with the latest GM software updates for your exact vehicle, ensuring optimal performance and fixing potential factory bugs.
- No Dealer Visit Required: Save hundreds of dollars and the hassle of having your car towed to a dealership for programming.
- Direct Fit and Function: This is an OEM part designed to meet the exact specifications for your Cadillac STS or CTS.
- Restored Drivability: Solves common issues related to stalling, rough running, and false sensor codes caused by a faulty computer.
Installation Process
The PCM on the 2005-2007 Cadillac STS with the 3.6L engine is located in the engine compartment on the right-hand (passenger) side. While the physical replacement is straightforward, please be aware that a security relearn procedure (often called a Passlock or anti-theft relearn) and a Crankshaft Variation (CASE) relearn will need to be performed after installation. These procedures can typically be done without a high-end scan tool and instructions are widely available online or in service manuals. This ensures the new PCM communicates correctly with your vehicle’s anti-theft system and crankshaft position sensor.
Fitment Information
This module is a direct replacement for vehicles with part number 12585814. Please verify that this part is correct for your specific vehicle before ordering.
- Cadillac STS: 2005, 2006, 2007 (with 3.6L V6 engine)
- Cadillac CTS: 2005 (Base model, with matching ID 12585814)
Frequently Asked Questions
Do I need to have this module programmed by a dealer?
No. We program the module to your vehicle’s specific VIN before we ship it. It arrives ready for installation and the subsequent security relearn procedure.
Is this a simple plug-and-play installation?
It is a direct physical fit, but it is not entirely plug-and-play. After installing the module, you MUST perform a security relearn and a CASE (Crankshaft Position Variation) relearn procedure for the vehicle to start and run correctly.
What happens if I forget to provide my VIN?
We cannot ship the PCM without your VIN. Programming is a mandatory part of this purchase, as the module will not function in your vehicle otherwise. We will contact you to retrieve the VIN if it is not provided at checkout.
Will this PCM fix my car’s specific problem?
This module will correct any issues directly caused by a faulty PCM. However, it is crucial that your vehicle is properly diagnosed. This part will not fix problems related to other bad sensors, wiring, or mechanical components.
Where is the PCM located on my 2006 Cadillac STS?
The PCM, or Electronic Control Module, is typically located in the engine compartment on the passenger side of the vehicle.
Are other part numbers compatible?
Yes, this module with part number 12585814 is also the correct service replacement for part numbers 12600940 and YHTZ for the specified applications.