Restore Your HUMMER’s Reliability with a Precision-Programmed Engine Computer
Is your 2009 or 2010 HUMMER H3 suffering from frustrating and unpredictable engine problems? Issues like sudden stalling, a persistent check engine light, rough idling, or a complete no-start condition often point directly to a failing Engine Control Module (ECM). As a technician with over two decades of experience, I’ve seen firsthand how a faulty ECM can cripple an otherwise solid vehicle. This isn’t just an inconvenience; it’s a matter of reliability and safety. This replacement ECM, part number 12636659, is the definitive solution to get your H3 running like it should.
The biggest hurdle when replacing a modern vehicle’s computer is the programming. Dealerships charge a premium for this service, and it requires specialized equipment. We eliminate that step entirely. When you purchase this module, you provide us with your vehicle’s VIN. Our experts then flash the computer with the latest, most stable General Motors software specific to your H3. It arrives at your door ready for a straightforward, plug-and-play installation, saving you time, money, and a trip to the service center. This is the most efficient way to solve complex electronic issues and restore your engine’s performance and fuel economy.
A Technician’s Notebook
I remember a 2009 H3 that came into the shop on a tow truck. The owner was frustrated because it would crank but never start, and he’d already replaced the battery and fuel pump. The scan tool showed a U0100 ‘Lost Communication with ECM’ code. After verifying power and ground at the ECM connector—a crucial first step—we knew the module itself was the culprit. The internal processor had failed. We installed a VIN-programmed ECM just like this one, and the truck fired up on the first try. It’s a classic failure mode, and having a pre-programmed unit turned a multi-day diagnostic and repair job into a simple afternoon fix.
Common Signs of a Failing ECM
If your vehicle is exhibiting any of these symptoms, a faulty engine computer is a likely cause. A failing 2009-2010 HUMMER H3 ECM can be difficult to diagnose, but these are the classic indicators:
- âś” Check Engine Light is on with codes like P0601, P0606, or U0100.
- âś” Engine stalls for no apparent reason, either while driving or at idle.
- âś” Vehicle cranks but will not start.
- âś” Noticeable drop in fuel efficiency.
- âś” Poor engine performance, hesitation, or misfires.
- âś” Transmission shifting issues or failure to go into gear.
- âś” Communication problems with diagnostic scan tools.
A Straightforward Guide to Installation
Installing your new 2009-2010 HUMMER H3 ECM is a job most DIYers can handle. On the H3, the ECM is conveniently located on the right-hand (passenger side) firewall. Follow these steps for a smooth installation:
- Safety First: Disconnect the negative terminal from your vehicle’s battery and wait at least 15 minutes to allow all modules to power down completely.
- Locate the ECM: Open the hood and find the ECM mounted to the passenger-side firewall in the engine bay.
- Disconnect Connectors: Carefully release the locking tabs on the electrical wiring harnesses 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. There are typically a few 10mm bolts holding it in place.
- Install the New Module: Mount your new, pre-programmed ECM onto the bracket and secure it with the bolts.
- Reconnect Everything: Firmly plug the wiring harnesses back into the new ECM until they click into place. Reconnect the negative battery terminal.
- Final Step: Some vehicles may require a security relearn procedure, which typically involves cycling the key. Your vehicle’s service manual will have the specific, simple steps if needed.
Verified Vehicle Compatibility
This module is a direct replacement for service number 12636659 and is interchangeable with 12639300, 1263605, 12628993, 12628911, 12625453, 12622175, 12630464, and 12678512. It is guaranteed to fit the following vehicles:
- HUMMER H3: 2009-2010 (3.7L, Located on RH firewall)
- Chevrolet Colorado: 2009-2012 (2.9L & 3.7L)
- GMC Canyon: 2009-2012 (2.9L & 3.7L)
- 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 Corvette: 2009 (ZR1)
- Chevrolet Trailblazer: 2009 (6.0L)
- GMC Envoy: 2009 (5.3L)
- Buick Lucerne: 2009-2011 (4.6L)
- Saab 9-7X: 2009
This is the reliable, no-hassle solution for your vehicle. By providing your VIN, you ensure you receive a perfectly matched and updated 2009-2010 HUMMER H3 ECM, ready to restore your truck’s proper function right out of the box.
Frequently Asked Questions
Why do you need my VIN?
Your VIN (Vehicle Identification Number) is essential for us to program the ECM with the exact software and calibrations your HUMMER H3 requires. This ensures perfect compatibility with your engine, transmission, and other options, making the installation plug-and-play.
Is this a difficult part to install myself?
Not at all. For most DIYers with basic hand tools, this is a straightforward job. The ECM is easily accessible on the passenger-side firewall. Since we pre-program it, you avoid the most complex part of the process. Just bolt it in, plug it in, and you’re set.
Will this fix my check engine light?
If the check engine light is caused by an internal failure of the ECM (common codes include P0601, P0606), then yes, this part will resolve the issue. We always recommend having the codes professionally scanned to confirm the diagnosis before ordering.
What if I order the wrong part?
By providing your VIN at checkout, we take the guesswork out of it. We verify that this part number (12636659 or its interchanges) is correct for your specific vehicle before we program and ship it, guaranteeing a perfect fit.