Restore Peak Performance and Reliability to Your GM Vehicle
Is your Cadillac, Chevy, or Hummer experiencing frustrating issues like stalling, erratic idling, a persistent check engine light, or a complete no-start condition? These are classic signs of a failing Engine Control Module (ECM), the critical computer that manages your vehicle’s engine performance, fuel economy, and emissions. Don’t let a faulty ECM keep you sidelined. This direct-fit 2009 XLR Engine Control Module, part number 12639300, is the definitive solution to get you back on the road with confidence.
Over my 20+ years in automotive diagnostics, I’ve seen firsthand how a failing ECM can cause a cascade of confusing problems that are often misdiagnosed. This isn’t just a replacement part; it’s the restoration of your vehicle’s core operational logic. We take the guesswork and hassle out of the repair by programming the module specifically for your vehicle using your VIN. This means it arrives at your door loaded with the latest official GM software updates, ready for a straightforward installation without requiring an expensive trip to the dealership for programming.
Common Signs of a Failing ECM
- ✔ Unexplained check engine light with communication codes like U0100 or internal processor fault codes like P0601 or P0606.
- ✔ Engine performance problems, such as poor acceleration, misfires, or reduced fuel efficiency.
- ✔ Intermittent or complete no-start conditions where the engine cranks but won’t turn over.
- ✔ The cooling fans run constantly, even when the engine is cold.
- ✔ Seemingly unrelated warning lights appearing on the dashboard.
- ✔ Harsh or incorrect shifting from the automatic transmission.
A Technician’s Notebook: The Ghost in the Machine
A 2009 Cadillac STS came into the shop with a complaint that stumped two other mechanics: it would randomly refuse to start, but only after being driven for about 20 minutes. There were no consistent trouble codes. We checked fuel pressure, spark, and wiring harnesses—all perfect. On a hunch, I monitored the ECM data stream during a test drive. Just as the customer described, after 15 minutes, the data feed for multiple sensors flatlined simultaneously right before it stalled. The ECM was failing internally under heat soak. Replacing it with a quality, correctly programmed unit like this one solved the problem instantly. It’s a reminder that intermittent electrical faults are often the toughest to crack, and a reliable module is non-negotiable.
A Straightforward Guide to Installation
- ✔ Safety First: Disconnect the negative terminal from your vehicle’s battery and secure it away from the post to prevent accidental reconnection.
- ✔ Locate the ECM: On the 2009 Cadillac XLR, the ECM is located in the right-hand front of the engine compartment. For other models, its location may vary (e.g., RH firewall, LH engine). Consult a repair manual if you are unsure.
- ✔ Disconnect Connectors: Carefully release the locking tabs on the electrical wiring harness connectors and pull them straight out from the module. Do not force them.
- ✔ Remove the Old Module: Unbolt the old ECM from its mounting bracket. Note the orientation of the module.
- ✔ Install the New Module: Mount your new, pre-programmed ECM in the same position and orientation. Secure the mounting bolts.
- ✔ Reconnect Everything: Firmly plug the wiring harnesses back into the new ECM until they click into place. Reconnect the negative battery terminal.
- ✔ Perform Relearn Procedure: While the module is programmed, a security or Crankshaft Variation (CASE) relearn may be necessary. For many GM vehicles, this can be initiated by turning the key to the ‘ON’ position for 10-15 minutes, then ‘OFF’ for 10 seconds, and repeating this cycle three times before starting the engine.
By providing your Vehicle Identification Number (VIN) at checkout, you ensure that the 2009 XLR Engine Control Module you receive is a perfect match, streamlining your repair and eliminating costly programming fees.
Verified Vehicle Compatibility
This ECM is a direct replacement for service numbers 12636659, 12639300, 1263605, 12628993, 12628911, 12625453, 12622175, 12630464, and 12678512. It fits a wide range of GM vehicles, including:
- Cadillac CTS (2009) 6.2L
- Cadillac DTS (2009-2011)
- Cadillac SRX (2009) 4.6L
- Cadillac STS (2009-2010) 4.4L, 4.6L
- Cadillac XLR (2009) ID 12636659 or 12625453
- Chevrolet Colorado (2009-2012) 2.9L, 3.7L
- Chevrolet Corvette (2009) ZR1
- Chevrolet Trailblazer (2009) 6.0L
- GMC Canyon (2009-2012) 2.9L, 3.7L
- GMC Envoy (2009) 5.3L
- Buick Lucerne (2009-2011) 4.6L
- Hummer H3 (2009-2010) 3.7L
- Saab 9-7X (2009)
Frequently Asked Questions
Frequently Asked Questions
Do I need to do any programming or flashing myself?
No. We handle all the programming for you before shipment. Simply provide your vehicle’s 17-digit VIN during checkout, and the module will arrive ready for installation with the latest GM software.
Where do I find my VIN?
Your VIN can be found on your vehicle’s registration, insurance card, or on a placard on the driver’s side of the dashboard visible through the windshield.
Is a CASE Relearn required after installation?
In many cases, a CASE (Crankshaft Position System Variation) relearn is recommended to prevent a P0315 trouble code. This procedure can often be done with a capable bi-directional scan tool or by following the vehicle’s specific manual relearn process.
Is this compatible with other part numbers?
Yes, this ECM is a direct replacement for several service numbers, including 12636659, 12628993, 12625453, and others listed in the compatibility section.
What if I have questions during my installation?
Our team of experienced automotive professionals is here to help. Contact us with any questions, and we’ll provide the expert support you need to complete your repair.