Is Your Hummer H3 Stalling, Running Rough, or Showing a Check Engine Light?
If you’re dealing with frustrating engine problems in your 2009 or 2010 Hummer H3, a failing Engine Control Module (ECM) is often the culprit. As a mechanic with over two decades of diagnostic experience, I’ve seen firsthand how a faulty ECM can cause a cascade of issues that seem impossible to pin down. You might be experiencing random stalling, poor fuel economy, shifting problems, or a persistent check engine light with communication error codes. This isn’t just an inconvenience; it’s a critical failure in your vehicle’s central computer.
The Dealership-Free Solution: A True Plug-and-Play ECM
Forget about towing your H3 to a dealership and paying hundreds in programming fees. We offer a direct, reliable solution. This ECM, part number 12678512, arrives at your doorstep fully programmed to your vehicle’s specific Vehicle Identification Number (VIN). We load the latest, most stable GM-approved software, ensuring your engine operates exactly as the manufacturer intended. This process corrects factory bugs and optimizes performance for a lasting repair.
Common Symptoms of a Failing Hummer H3 ECM:
- ✔ Persistent Check Engine Light (CEL)
- ✔ Engine stalling or cutting out unexpectedly
- ✔ No-start or hard-starting conditions
- ✔ Noticeable decrease in fuel mileage
- ✔ Communication errors with diagnostic scan tools (e.g., U-codes)
- ✔ Harsh or erratic automatic transmission shifting
- ✔ Misfire codes that don’t resolve with new plugs or coils
From the Shop Floor: A Real-World Diagnostic Story
“A customer’s 2009 Hummer H3 came into my shop last month with a persistent P0606 (ECM Processor Fault) code that two other shops couldn’t solve. They’d replaced sensors and checked wiring, but the issue was a failing processor inside the original module. After installing one of our pre-programmed ECMs and performing the simple security relearn, the truck ran perfectly, and the code never returned. This is a classic case where swapping parts doesn’t work, but replacing the brain of the engine does.”
Easy Installation Guide for Your 2009–2010 Hummer H3 Engine Control Module
You don’t need to be a master technician to install this part. With basic tools, you can have your H3 running smoothly again. The ECM is located on the passenger side of the vehicle, mounted to the firewall.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery before beginning work.
- Locate the ECM: Open the hood and find the ECM on the right-hand (passenger side) firewall.
- Disconnect Connectors: Carefully unlatch and remove the electrical wiring harness connectors. These have locking tabs, so be gentle to avoid breaking them.
- Remove the Old Module: Unbolt the old ECM from its mounting bracket on the firewall and remove it from the vehicle.
- Install the New ECM: Mount your new, pre-programmed ECM in the same location and secure it with the bolts.
- Reconnect Everything: Plug the wiring harness connectors firmly back into the new module until they click into place. Reconnect the negative battery terminal.
- Perform Security Relearn (Required): This final step syncs the new ECM with your vehicle’s anti-theft system. Simply turn the key to the ‘ON’ position for 10 minutes, ‘OFF’ for 10 seconds, and repeat this cycle two more times for a total of 30 minutes. Your H3 should then start and run correctly.
Guaranteed Compatibility & Quality
This module is a direct replacement for a wide range of GM vehicles, confirming its robust design. It is fully interchangeable with the following service part numbers:
12636659, 12639300, 1263605, 12628993, 12628911, 12625453, 12622175, 12630464, and 12678512.
Provide us with your VIN at checkout, and we’ll handle the rest. Restore your Hummer’s reliability and performance with a solution that’s built to last.