Restore Peak Performance to Your Cadillac or Pontiac
Is your 2004 Cadillac Seville, DeVille, or 2004-2005 Pontiac Bonneville suffering from perplexing engine issues? Unexplained stalling, poor fuel economy, a persistent check engine light, or a no-start condition can often be traced back to a failing Powertrain Control Module (PCM). This module is the brain of your vehicle’s engine and transmission, and when it falters, the entire driving experience is compromised. This listing offers a direct, reliable solution: a genuine used GM PCM, part number 12587465, professionally programmed to your vehicle’s specific Vehicle Identification Number (VIN).
Why a Programmed PCM is Essential
Unlike a generic part off the shelf, this PCM is not plug-and-play until it’s specifically calibrated for your car. Modern vehicles have complex anti-theft systems and specific operational parameters tied to the VIN. Our process ensures a seamless integration. We flash the module with the latest official GM software updates using your VIN, which corrects factory bugs and optimizes performance. This critical step ensures the PCM communicates perfectly with your vehicle’s other modules, restoring its original factory operation and preventing compatibility issues that can arise from using an unprogrammed unit.
From the Diagnostic Bay
We had a 2004 Cadillac DeVille come into the shop with a ghost of a problem. The owner complained of intermittent stalling at stoplights and a hesitation on acceleration that no one could pinpoint. We checked the fuel system, ignition components, and sensors—all tested fine. There were no consistent trouble codes, just a few random communication errors. After exhausting the usual suspects, we focused on the brain itself. We swapped in a known-good, VIN-programmed PCM like this one. The change was immediate. The stalling vanished, the throttle response was crisp, and the car ran like it just left the showroom. It’s a powerful reminder that when the vehicle’s computer isn’t functioning at 100%, it can create symptoms that mimic a dozen other failures.
Common Symptoms of a Failing Powertrain Control Module
- ✔ Persistent Check Engine Light (CEL) illumination
- ✔ Engine stalling or shutting off while driving
- ✔ Rough idling or engine misfires
- ✔ Difficulty starting the engine or a complete no-start condition
- ✔ Noticeable decrease in fuel efficiency
- ✔ Harsh or erratic automatic transmission shifting
- ✔ Failure to pass state emissions testing
- ✔ Unresponsive throttle or poor acceleration
Direct Fitment and Function for Your 2004 Seville PCM
This engine control module is a guaranteed fit for the following vehicles, provided the part number matches. It is a direct replacement for service numbers 12587465, 12586547, and 15576920.
- 2004-2005 Pontiac Bonneville: (Located in LH engine compartment), with 4.6L engine
- 2004-2005 Cadillac DeVille: (Located in LH engine compartment)
- 2004 Cadillac Seville: (Located in LH engine compartment)
IMPORTANT: After purchasing, you must provide us with your vehicle’s 17-digit VIN. This is absolutely necessary for us to program the module before shipment. Failure to provide the VIN will result in a delay. Please add your VIN to the ‘notes’ section during checkout or send us a message immediately after your order.
Frequently Asked Questions
What is a PCM and what does it do?
The Powertrain Control Module (PCM), often called the Engine Control Module (ECM) or Engine Control Unit (ECU), is your vehicle’s main computer. It controls all aspects of engine performance, including fuel injection, ignition timing, emissions systems, and automatic transmission shifting, to ensure optimal power, efficiency, and low emissions.
Is this part ready to install when it arrives?
Yes. Because we program it to your specific VIN before shipping, it is ready to be installed. In most cases, this eliminates the need for expensive programming at a dealership. However, you may need to perform a simple security relearn procedure after installation.
How do I provide my VIN?
You can enter your 17-digit VIN in the ‘notes to seller’ box during the checkout process. If you miss it, you can also send us a direct message with your VIN immediately after placing your order. We cannot ship the part until we have this information.
Will I need to do anything after installation?
After installing the PCM, you will likely need to perform a security relearn procedure, sometimes called a CASE relearn or anti-theft relearn. This procedure syncs the new PCM with your vehicle’s keys and security system. It is a standard process for GM vehicles and can often be done without special tools. Instructions can be readily found online for your specific model.
Is this a new part?
No, this is a thoroughly inspected and tested used OEM part sourced from a salvaged vehicle. This provides the reliability of a genuine GM component at a significant cost saving compared to a new part from a dealer.
What other part numbers does this PCM replace?
This PCM, service number 12587465, is a direct replacement for modules with service numbers 12586547 and 15576920. Please verify your original part number to ensure compatibility.