Restore Peak Performance to Your Northstar V8
Is your 2004 Cadillac Seville, DeVille, or 2004-2005 Pontiac Bonneville suffering from perplexing engine issues? A faulty Powertrain Control Module (PCM), also known as an Engine Control Module (ECM), is often the culprit behind problems that defy simple diagnosis. This module is the electronic brain of your vehicle, managing everything from fuel injection and ignition timing to transmission shifting and emissions control. When it fails, the symptoms can be widespread and frustrating. This listing is for a genuine, used GM PCM with service number 12587465, a direct replacement for your vehicle that arrives programmed and ready for installation.
From the Diagnostic Bay
We had a 2004 Cadillac DeVille come into the shop with a complaint of intermittent stalling at stoplights and a persistent Check Engine Light. The owner had already replaced the crankshaft position sensor and cleaned the throttle body with no success. Our scan tool showed a loss of communication with the PCM (U-series codes). After verifying the power and ground circuits to the module were solid, we knew the internal logic of the original computer was failing. We installed a VIN-programmed PCM just like this one, performed the security relearn, and the car ran perfectly. It’s a classic case where swapping the central component is the only correct fix.
Is Your Vehicle Showing Signs of PCM Failure?
A failing engine computer can manifest in numerous ways. If you’re experiencing any of the following, it might be time to consider replacing your 2004 Seville PCM. Look out for these common indicators:
- ✔ Check Engine Light: The light is on, and you may have codes related to module communication, sensor reference voltage, or internal processor faults.
- ✔ No-Start or Hard-Start Condition: The engine cranks but refuses to start, or takes an excessively long time to fire up.
- ✔ Poor Engine Performance: Noticeable loss of power, hesitation during acceleration, or rough idling.
- ✔ Reduced Fuel Economy: A sudden and unexplained drop in your vehicle’s MPG can be linked to incorrect fuel and air calculations from a faulty PCM.
- ✔ Erratic Transmission Shifting: Harsh shifts, delayed engagement, or getting stuck in a gear can be caused by the PCM failing to communicate properly with the transmission control module.
- ✔ Intermittent Stalling: The engine shuts off unexpectedly while driving or idling.
A Plug-and-Play Solution for Your 2004 Seville PCM
Don’t let a bad engine computer keep your luxury sedan off the road. This replacement module is the most straightforward and reliable way to solve your vehicle’s electronic issues. We take a high-quality, used OEM unit and flash it with the latest official GM software updates specifically for your car. This critical programming service, performed before we ship, ensures that the module communicates perfectly with your vehicle’s existing systems right out of the box. Simply provide us with your Vehicle Identification Number (VIN) after purchase, and we’ll handle the rest.
This module, part number 12587465, is a direct replacement for the following service numbers: 12587465, 12586547, and 15576920. It is located in the left-hand (driver’s side) engine compartment.
Fitment Guarantee:
- Cadillac Seville: 2004 (Electronic Control Module; LH engine compartment)
- Cadillac DeVille: 2004 (Electronic Control Module; LH engine compartment)
- Cadillac DeVille: 2005 (Electronic Control Module; LH engine compartment, ID 12587465)
- Pontiac Bonneville: 2004-2005 (Electronic Control Module; LH engine compartment, 4.6L)
Frequently Asked Questions
What information do you need to program the PCM?
We require your vehicle’s 17-digit Vehicle Identification Number (VIN) to program the module correctly. This ensures it has the right software for your car’s specific options and systems. Please provide your VIN during or after checkout.
Is this a new part?
No, this is a genuine, used OEM part sourced from a salvaged vehicle. Each unit is inspected and tested to ensure it is fully functional before being programmed and shipped.
Will I need to do anything after installing this PCM?
In most cases, you will need to perform a security relearn procedure (often called a CASE relearn or Passlock relearn). This syncs the new PCM with your vehicle’s anti-theft system. This procedure can often be completed without special tools and instructions can be readily found online for your specific model.
How can I be sure the PCM is the problem?
While the symptoms listed are strong indicators of PCM failure, they can also be caused by wiring issues or faulty sensors. We always recommend a thorough diagnosis by a qualified mechanic to confirm the PCM is the point of failure before ordering a replacement.
Why is VIN programming so important?
VIN programming loads the correct software and calibrations for your vehicle’s engine, transmission, and options package. An unprogrammed module from a different vehicle will not work correctly and will likely cause a no-start condition and multiple error codes.