Restore Peak Performance and Reliability to Your Hummer H3
If you’re dealing with frustrating and unpredictable engine problems in your 2009-2010 Hummer H3—like stalling, rough idling, a persistent check engine light, or a complete no-start condition—a failing Engine Control Module (ECM) is often the culprit. This isn’t just an inconvenience; it’s a critical component failure that compromises your vehicle’s performance and safety. This replacement ECM, part number 12678512, is the definitive solution to get your rugged H3 back on the road and running exactly as it should.
The biggest challenge with replacing a modern ECM is the complex programming required to sync it with your vehicle’s specific systems. We eliminate that expensive and time-consuming step for you. Before we ship your part, we flash it with the latest official GM software updates, precisely matched to your vehicle using the VIN you provide. This means your new 2009-2010 Hummer H3 ECM arrives ready for a straightforward installation, saving you a costly trip to the dealership and hours of diagnostic headaches.
From the Diagnostic Bay: The Ghost in the Machine
I remember a 2010 Hummer H3 that came into my shop with a laundry list of bizarre, intermittent issues. The owner was frustrated; he’d already replaced the throttle body and a couple of sensors based on codes that would pop up and disappear. The truck would run fine for days, then suddenly go into reduced power mode or refuse to shift correctly. After checking all the wiring and grounds, my experience pointed to the ECM. These modules can develop internal faults that don’t always throw a clear P0601 ‘bad module’ code. Instead, they send out faulty signals, making other perfectly good components look like the problem. Installing a VIN-programmed ECM resolved every single issue instantly. It’s a classic case where chasing individual codes costs more time and money than addressing the root cause: the vehicle’s brain.
Is Your H3 Showing These Telltale Signs?
A failing ECM can manifest in numerous ways. If you’re experiencing any of the following, it’s a strong indicator that your engine’s computer needs attention:
- ✔ Unexplained Check Engine Light (CEL) illumination
- ✔ Engine stalling or shutting off while driving
- ✔ No-start or hard-starting conditions
- ✔ Noticeable drop in fuel economy
- ✔ Poor acceleration or engine hesitation
- ✔ Erratic transmission shifting behavior
- ✔ Diagnostic Trouble Codes (DTCs) related to internal module failure (e.g., P0601, P0606) or communication errors (U0100).
A Straightforward Guide to Installation
With our pre-programming service, installing your new 2009-2010 Hummer H3 ECM is a manageable job for a DIY enthusiast. Follow these steps carefully for a successful replacement.
- 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 Hummer H3, the ECM is typically located on the right-hand (passenger) side of the firewall in the engine bay.
- Disconnect the Harnesses: Carefully release the locking tabs on the electrical wiring harnesses connected to the old ECM and gently pull them straight out. Avoid damaging the pins or connectors.
- Remove the Old Module: Unbolt the mounting hardware holding the old ECM in place and remove it from the vehicle.
- Install the New Module: Mount your new, pre-programmed ECM in the same location and secure it with the original hardware.
- Reconnect Everything: Firmly plug the wiring harnesses into the new ECM, ensuring the locking tabs click into place. Reconnect the negative battery terminal.
- Final Step: In some cases, a security or anti-theft relearn procedure may be required. This can typically be done without special tools by cycling the key. Consult your vehicle’s service manual for the specific procedure.
By purchasing this module, you are getting a reliable part that restores function and peace of mind, backed by a service that simplifies the entire repair process. This is more than just a part; it’s a complete solution for your 2009-2010 Hummer H3 ECM problems.
Verified Vehicle Compatibility
This Engine Control Module is a direct replacement for service number 12678512 and is also interchangeable with part numbers 12636659, 12639300, 1263605, 12628993, 12628911, 12625453, 12622175, and 12630464. It is guaranteed to fit the following vehicles:
- ✔ 2009-2010 HUMMER H3 (3.7L & others)
- ✔ 2010-2012 CHEVROLET COLORADO (2.9L, 3.7L)
- ✔ 2009 CHEVROLET COLORADO
- ✔ 2010-2012 GMC CANYON (2.9L, 3.7L)
- ✔ 2009 GMC CANYON
- ✔ 2009 CHEVROLET TRAILBLAZER (6.0L)
- ✔ 2009 GMC ENVOY (5.3L)
- ✔ 2009 SAAB 9-7X
- ✔ 2009 CADILLAC CTS (6.2L)
- ✔ 2009-2011 CADILLAC DTS
- ✔ 2009 CADILLAC SRX (4.6L)
- ✔ 2009-2010 CADILLAC STS (4.4L, 4.6L)
- ✔ 2009 CADILLAC XLR
- ✔ 2009 CHEVROLET CORVETTE (ZR1)
- ✔ 2009-2011 BUICK LUCERNE (4.6L)
Frequently Asked Questions
Do I really need to provide my VIN?
Yes, providing your Vehicle Identification Number (VIN) is mandatory. This allows us to program the module with the correct software for your H3’s specific options, engine, and transmission, ensuring it works perfectly right out of the box.
Is any additional programming required after installation?
No, the core engine and transmission programming is completed by us before shipping. In some cases, a simple key-cycle anti-theft relearn procedure may be necessary, which you can do yourself in minutes.
Will this fix my check engine light?
If the check engine light and other symptoms are caused by a faulty ECM, then yes, this part will resolve those issues. It is crucial to ensure the ECM is the true source of the problem before ordering.
Is this a new or used part?
This is a high-quality, tested, and verified used OEM part. Each module is thoroughly inspected and then programmed with the latest GM software to ensure it meets or exceeds original performance standards.
What if I have a different part number on my original module?
Our module, 12678512, is interchangeable with a wide range of GM service numbers. Please check the list of compatible part numbers in our description to confirm it will work for your vehicle.