Restore Peak Performance to Your 2009-2010 Hummer H3
Is your Hummer H3 suffering from frustrating issues like intermittent stalling, a persistent Check Engine Light, rough idling, or a complete no-start condition? These are classic signs of a failing Engine Control Module (ECM). As the brain of your vehicle, a faulty ECM can disrupt everything from fuel delivery and ignition timing to transmission shifting, leaving you stranded and facing a costly trip to the dealership. This isn’t just an inconvenience; it’s a reliability issue that needs a solid fix.
This is a direct-replacement Hummer H3 Engine Control Module, service part number 12639300, that arrives at your door ready for installation. The biggest hurdle with ECM replacement is the need for expensive, dealer-specific programming. We eliminate that completely. When you place your order, simply provide us with your vehicle’s VIN. Our technicians will then flash the module with the latest, most stable GM-approved software specific to your H3. This ensures seamless communication with all other modules in your vehicle and restores the original factory performance and fuel efficiency standards.
Case Study: A Tricky Diagnosis
A few months back, a 2010 H3 was towed into my bay. The owner was frustrated; it would start and run fine for 10 minutes, then suddenly die and refuse to restart for an hour. No consistent Check Engine Light, just a random U0100 (Lost Communication with ECM) code stored in the BCM. After verifying power and ground integrity to the ECM—a critical first step I always recommend—we hooked up a scope. We found the 5-volt reference signal would drop out precisely when the engine warmed up. This pointed directly to an internal failure in the original ECM, a common issue caused by heat cycles and vibration over thousands of miles. Swapping in a properly programmed module like this one had the truck running reliably in under an hour. It’s a textbook example of how a failing ECM can cause ghost-like, intermittent problems that are maddening to diagnose without experience.
Is Your H3 Showing These Symptoms?
A failing ECM can manifest in numerous ways. If you’re experiencing any of the following, this module is the likely solution:
- ✔ Check Engine Light is on with codes pointing to internal module failure (e.g., P0601, P0606).
- ✔ Engine cranks but will not start.
- ✔ Intermittent stalling, especially after the engine warms up.
- ✔ Noticeable decrease in fuel economy.
- ✔ Poor engine performance, hesitation, or misfiring.
- ✔ Communication errors with scan tools or other vehicle modules (U-codes).
- ✔ Harsh or erratic automatic transmission shifting.
A Straightforward Guide to Installation
Installing your new Hummer H3 Engine Control Module is a job most DIYers can handle with basic tools. In the H3, the ECM is conveniently located on the passenger side (RH) firewall in the engine bay.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery and wait at least 15 minutes for all module capacitors to discharge.
- Locate the ECM: Open the hood and find the module on the right-hand firewall. It will have several large electrical connectors attached.
- Disconnect the Connectors: Carefully release the locking tabs on each wiring harness connector and pull them straight out from the module. Avoid pulling on the wires themselves.
- Remove the Old Module: Unbolt the old ECM from its mounting bracket on the firewall.
- Install the New Module: Mount your new, pre-programmed ECM onto the bracket and secure the bolts.
- Reconnect Everything: Plug the wiring harness connectors firmly back into the new module until they click into place. Reconnect your negative battery terminal.
- Final Step: In some cases, a security relearn procedure may be necessary. This can typically be done by turning the key to the ‘ON’ position for 10-15 minutes, then off, and repeating two more times before starting the engine.
Verified Vehicle Compatibility
This module is a guaranteed fit for a wide range of GM vehicles. It is a direct replacement for the following service part numbers: 12636659, 12639300, 1263605, 12628993, 12628911, 12625453, 12622175, 12630464, and 12678512.
It will fit the following makes and models equipped with the specified options:
- HUMMER H3: 2009-2010 (RH firewall)
- Chevrolet Colorado / GMC Canyon: 2009-2012 (RH firewall)
- Chevrolet Trailblazer / GMC Envoy: 2009 (LH engine)
- Saab 9-7X: 2009 (LH engine)
- Cadillac CTS, STS, SRX, XLR: 2009-2010 (Various locations)
- Buick Lucerne / Cadillac DTS: 2009-2011
- Chevrolet Corvette: 2009 (ZR1)
Please confirm your vehicle and part number before ordering. If you’re unsure, send us a message with your VIN, and we’ll be happy to verify compatibility for you.
Do I need to do any programming after I receive this ECM?
Do I need to do any programming after I receive this ECM?
No. We program the module to your specific vehicle using the VIN you provide during checkout. It arrives ready to install, saving you a trip to the dealer for programming.
Where do I provide my VIN?
You can add your VIN in the notes section during checkout or send it to us in a message after you place your order. We cannot ship the module until we have your VIN to ensure correct programming.
Is this a brand new part?
This is a high-quality, tested, and guaranteed used OEM part. Each module is thoroughly inspected and then loaded with the latest GM software for your vehicle, ensuring reliable performance.
Will this fix my Check Engine Light?
If the Check Engine Light is caused by an internal ECM failure (like DTC P0601), then yes, this part will resolve the issue. However, you should always ensure that the root cause of the problem is the ECM and not a separate sensor or wiring issue.
What is the security relearn procedure?
Most GM vehicles of this era have a simple anti-theft relearn process. After installation, you typically turn the key to the ‘ON’ position (without starting) for 10 minutes, then ‘OFF’ for 10 seconds. Repeat this cycle three times. This allows the new ECM to synchronize with your vehicle’s security system.