Restore Your HUMMER’s Performance and Reliability
Is your 2009 HUMMER H2 running rough, refusing to start, or showing a persistent Check Engine Light? As a technician with over two decades of experience under the hood, I’ve seen firsthand how a failing Engine Control Module (ECM) can cause a host of frustrating and hard-to-diagnose issues. It’s the brain of your vehicle, and when it falters, everything from fuel economy to transmission shifting can suffer. This isn’t just an inconvenience; it’s a critical component failure that can leave you stranded. This replacement Engine Computer is the definitive solution to get your H2 operating like it should.
We take the guesswork and extra cost out of the repair. Unlike a generic part from a salvage yard or a big-box store, this module arrives at your door specifically programmed for your vehicle. Simply provide us with your Vehicle Identification Number (VIN) after purchase, and our experts will flash the unit with the latest, most stable GM software updates. This ensures seamless communication with your vehicle’s other modules and restores original factory performance. This is the exact process we use in the shop to guarantee a successful repair, and now you can get that same level of precision delivered directly to you.
Case Study: The Misleading No-Start
A customer brought in a 2009 Sierra 2500 (which uses this same ECM family) with an intermittent no-start condition. They had already replaced the battery and the fuel pump, but the problem persisted. After connecting my scan tool, I noticed a U0100 Lost Communication with ECM code, but it wasn’t consistent. The real clue came from monitoring the 5-volt reference signal from the ECM—it was dropping out randomly. Instead of chasing sensors, we went straight to the source. A failing processor inside the original ECM was overheating and shutting down, cutting power to critical sensors. Installing a correctly programmed 2009 HUMMER H2 Engine Computer (in that case, for a Sierra) solved the problem instantly. This highlights why throwing parts at an issue is costly; a proper diagnosis points to the core component.
Is Your H2 Showing These Signs of a Bad ECM?
A failing engine computer can manifest in numerous ways. If you’re experiencing any of the following, a faulty ECM is a likely culprit:
- ✔ Check Engine Light is on with communication-related codes (like U0100) or internal processor fault codes (like P0601, P0606).
- ✔ The engine cranks but will not start, even with good fuel pressure and spark.
- ✔ Unexplained drop in fuel efficiency or engine performance.
- ✔ Intermittent stalling, rough idling, or engine hesitation.
- ✔ Automatic transmission shifting issues or harsh engagement.
- ✔ Other modules on the vehicle cannot communicate with the engine computer.
A Straightforward Guide to Installation
This repair is well within the reach of a DIY enthusiast. With basic hand tools, you can have your HUMMER back on the road in under an hour. Follow these steps for a smooth installation:
- Safety First: Always disconnect the negative terminal from your vehicle’s battery and wait 10 minutes for the system to fully discharge.
- Locate the ECM: On the 2009 HUMMER H2, the Engine Control Module is typically found in the engine compartment on the driver’s side (LH side), often near the firewall or inner fender.
- Disconnect the Wiring: Carefully release the locking tabs on the electrical connectors and pull them straight out from the module. Never force them. Inspect the connectors for any corrosion or damage.
- Remove the Old Module: Unbolt the old ECM from its mounting bracket. Keep the hardware as you will need it for the new unit.
- Install the New ECM: Mount your new, pre-programmed ECM onto the bracket and secure it with the original bolts.
- Reconnect Everything: Plug the wiring harnesses back into the new module until they click securely into place. Reconnect the negative battery terminal.
- Final Steps: 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 then starting the vehicle. Your H2 is now ready to drive!
Verified Vehicle Compatibility
This module, part number 12629009, is a direct replacement for service number 12625455 and fits a wide range of GM vehicles. While this listing is for a 2009 HUMMER H2 Engine Computer, it is also confirmed to fit the following models. Please verify your specific vehicle and options:
H2 2009 (LH front engine compartment)
CADILLAC:
ESCALADE / ESV / EXT 2009-2010
CHEVROLET:
AVALANCHE 1500 2009-2010
CORVETTE 2009 (Base, RH engine compartment)
EXPRESS / SAVANA VANS (1500, 2500, 3500) 2009
IMPALA 2009 (3.5L, 3.9L)
MALIBU 2009 (3.5L)
SILVERADO (1500, 2500, 3500) 2009-2010
SUBURBAN (1500, 2500) 2009-2010
TAHOE 2009-2010
GMC:
SIERRA (1500, 2500, 3500, Denali) 2009-2010
YUKON / YUKON XL (1500, 2500) 2009-2010
PONTIAC:
G6 2009 (3.5L, 3.9L)
G8 2009
SATURN:
VUE 2010 (3.5L)
Frequently Asked Questions
Do I need to get this computer programmed?
No. This is the biggest benefit of our service. We program the engine computer to your vehicle’s specific VIN before we ship it. It arrives ready for installation, saving you a trip to the dealership and avoiding expensive programming fees.
What information do you need from me?
After you complete your purchase, you will need to provide us with your 17-digit Vehicle Identification Number (VIN). You can find this on your vehicle’s registration, insurance card, or on the driver’s side dashboard viewable through the windshield.
Is this a difficult part to replace myself?
For most of the vehicles this fits, the ECM is very accessible in the engine bay and is held in by a few bolts. As long as you are comfortable disconnecting the battery and using basic hand tools, this is a very manageable DIY job.
How do I know for sure my old ECM is bad?
The best way to be 100% certain is a professional diagnosis. However, symptoms like a no-start condition with no spark or injector pulse, or specific diagnostic trouble codes like P0601 (Internal Memory Failure), are very strong indicators of a failed ECM.
Will this fix my transmission shifting problems?
In many cases, yes. The ECM works directly with the Transmission Control Module (TCM) to manage shift points. If the ECM is sending bad data or has failed, it can absolutely cause poor shifting performance. Replacing a faulty ECM often resolves these related issues.