Is Your Cadillac Seville Running Rough? The PCM Might Be the Culprit.
If your 2004 Cadillac Seville is experiencing perplexing issues like erratic idling, poor fuel economy, harsh shifting, or a dreaded no-start condition, the problem might lie with its central nervous system: the Powertrain Control Module (PCM). This vital component, also known as an engine computer, is responsible for managing everything from fuel injection and ignition timing to transmission shift points. When it fails, it can cause a cascade of problems that can be difficult to diagnose. Don’t let a faulty computer keep your luxury sedan off the road. This is your direct-fit, plug-and-play solution.
From the Diagnostic Bay
We had a 2004 Seville towed in that had every mechanic who looked at it stumped. The owner had replaced the spark plugs, ignition coils, and even the fuel pump. The car would start sometimes but run terribly, and other times it wouldn’t start at all. It was throwing a mix of communication codes (U-codes) and random sensor codes. After hours of chasing wires, we finally hooked up our scope to the PCM’s main outputs. The signals were erratic and inconsistent. We installed one of our pre-programmed modules, and the car fired up instantly and idled perfectly. It was a classic case of an internally failing 2004 Seville PCM that was slowly losing its mind and taking the rest of the car’s systems with it.
Symptoms of a Failing 2004 Seville PCM
- ✔ Check Engine Light is on with codes pointing to internal module failure (e.g., P0601, P0606).
- ✔ Unexplained stalling or difficulty starting the engine.
- ✔ Noticeable decrease in fuel efficiency.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ Engine misfires, stumbles, or hesitates during acceleration.
- ✔ Failure of emissions testing due to PCM-related faults.
- ✔ Intermittent electrical issues that seem to have no other cause.
The Simple, Reliable Solution: Pre-Programmed and Ready to Install
Replacing a PCM used to mean a costly trip to the dealership for installation and programming. We’ve eliminated that hassle. This genuine, used GM PCM, part number 12587465, is sourced from a salvaged vehicle and meticulously inspected. The real value is in our service: before we ship it, we flash the module with the latest GM software updates and program it specifically to your vehicle’s Vehicle Identification Number (VIN). This ensures that when it arrives, it’s a true plug-and-play part. Simply disconnect the battery, swap the modules, reconnect the battery, and perform any necessary security relearn procedure. You’ll restore your vehicle’s original performance and reliability without the dealership price tag.
Guaranteed Fitment
This module is a direct replacement for service numbers 12587465, 12586547, and 15576920. Please verify your part number before ordering. This part is confirmed to fit the following vehicles:
- Cadillac Seville: 2004 (Electronic Control Module; LH engine compartment)
- Cadillac DeVille: 2004-2005 (Electronic Control Module; LH engine compartment, 2005 requires ID 12587465)
- Pontiac Bonneville: 2004-2005 (Electronic Control Module; LH engine compartment, 4.6L)
IMPORTANT: After completing your purchase, you MUST provide us with your vehicle’s VIN. We cannot ship your order until we have this information to program the module correctly.
Frequently Asked Questions
Do I need to have this computer programmed by a dealer?
No. We handle the programming for you before shipment. We flash it with the latest GM updates and program it to your specific VIN, making it ready for installation right out of the box.
Is this a new part?
No, this is a high-quality, tested, used part that has been recovered from a salvaged vehicle. This allows us to offer a reliable, factory component at a significant savings compared to a new unit.
What happens if I forget to provide my VIN?
Your order will be placed on hold. We cannot ship the PCM without your VIN because the programming is essential for the part to function correctly in your vehicle. We will contact you to retrieve the VIN before processing the order.
Will this fix my transmission problems?
It certainly can. The Powertrain Control Module (PCM) on these vehicles controls both the engine and the transmission. A failing PCM is a common cause of erratic shifting, delayed engagement, and other transmission-related issues.
What is the security relearn procedure?
After installation, you may need to perform a security relearn (also known as a VATS relearn) to allow your car’s anti-theft system to recognize the new PCM. This is a simple procedure that typically involves turning the key to the ‘ON’ position for 10-15 minutes, then off, and repeating two more times. Instructions can be easily found online for your specific model.