Restore Your Vehicle’s Brain and Get Back on the Road
Is your 2009 Trailblazer or other GM vehicle acting erratically? Stalling, poor fuel mileage, a persistent Check Engine Light, or a complete no-start condition can often be traced back to a failing Engine Control Module (ECM). As the central computer of your vehicle, a faulty ECM can cause a cascade of frustrating and hard-to-diagnose problems. This isn’t just an inconvenience; it’s a critical failure that compromises your vehicle’s performance and reliability. We offer a direct, dependable solution: a high-quality replacement ECM, part number 12636659, delivered to your door fully programmed for your specific vehicle.
Case Study: A Tricky Diagnosis
I remember a 2009 Trailblazer 6.0L that came into my shop with a complaint of intermittent stalling at stoplights and random warning lights on the dash. The owner had already replaced the alternator and battery with no success. My initial scan showed a handful of communication codes (U-codes) but nothing pointing directly to a single component. After checking the main power and ground circuits to the ECM, which is a critical first step, I noticed the 5-volt reference signal was fluctuating slightly. This is a classic sign of an internal ECM short. We installed a VIN-programmed 2009 Trailblazer Engine Control Module, performed the security relearn, and the truck ran perfectly. The customer saved hundreds compared to the dealership quote and avoided weeks of guesswork.
Is Your Vehicle Showing These Symptoms?
A failing ECM can manifest in many ways. If you’re experiencing any of the following, it might be time for a replacement. In my 20+ years of experience, these are the most common indicators:
- âś” Check Engine Light is on with codes like P0601, P0606, or P060A (Internal Control Module Processor Performance).
- âś” Engine cranks but refuses to start.
- âś” Intermittent stalling or rough idling for no apparent reason.
- âś” A noticeable drop in fuel economy.
- âś” Transmission shifting problems or getting stuck in one gear.
- âś” Communication errors with your scan tool (e.g., U0100 – Lost Communication with ECM).
- âś” Apparent failure of multiple sensors at once.
A Straightforward Guide to Installation
Replacing your ECM is a job most DIYers with basic tools can handle. Our pre-programming service eliminates the most difficult step, saving you a trip to the dealer. Here is a general guide:
- Safety First: Always disconnect the negative terminal from your vehicle’s battery and wait at least 10 minutes to allow capacitors to discharge.
- Locate the ECM: On the 2009 Trailblazer, the ECM is typically located on the driver’s side of the engine. On other models, it could be on the firewall or frame rail (refer to your service manual for the exact location).
- Disconnect Connectors: Carefully release the locking tabs on the electrical wiring harnesses and pull them straight out from the module. Do not force them.
- Remove the Old Module: Unbolt the old ECM from its mounting bracket.
- Install the New Module: Bolt the new ECM into place and securely reconnect the wiring harnesses. You should hear a ‘click’ as they lock in.
- Reconnect Battery: Re-attach the negative battery terminal.
- Perform Security Relearn: Most GM vehicles require a security relearn procedure. This can often be done without a scan tool by turning the key to the ‘ON’ position for 10-15 minutes, then ‘OFF’ for 10 seconds, and repeating this cycle three times. Your vehicle should then start.
Guaranteed Fitment for Your GM Vehicle
This 2009 Trailblazer Engine Control Module is a direct replacement for service number 12636659 and is also interchangeable with part numbers 12639300, 1263605, 12628993, 12628911, 12625453, 12622175, 12630464, and 12678512. It is confirmed to fit the following vehicles:
ENVOY 09 (LH engine), 5.3L
SAAB 9-7X 09 (LH engine)
CORVETTE 09 (RH engine compartment), ZR1
CTS 09 (RH front engine compartment), 6.2L
XLR 09 (RH front engine compartment), ID 12636659 or 12625453
STS 09 (LH frame rail), 4.4L or 4.6L
STS 10 (LH frame rail), 4.6L
SRX 09 (LH engine compartment), 4.6L
DTS 09-11
LUCERNE 09-11 (lower part of air cleaner box), 4.6L
HUMMER H3 09-10 (RH firewall)
COLORADO 09-12 (RH firewall), 2.9L or 3.7L
CANYON 09-12 (RH firewall), 2.9L or 3.7L
Frequently Asked Questions
What does ‘VIN Programmed’ mean?
It means we load the latest GM-certified software for your specific vehicle directly onto the module using your Vehicle Identification Number (VIN). This ensures the ECM communicates perfectly with your engine, transmission, and security system, making it a true plug-and-play part.
Will I need a mechanic to install this?
While professional installation is always an option, this is a very DIY-friendly repair. Because we handle the programming, you just need basic hand tools to swap the module and perform the simple key-cycle security relearn procedure.
How do I provide my VIN?
After you complete your purchase, you will need to send us your 17-digit VIN. We cannot ship the module until we have this information to complete the programming.
My original part number is different but on your interchange list. Will this work?
Yes. Manufacturers often update part numbers over time. The numbers listed (like 12639300, 12628993, etc.) are all superseded or interchangeable service numbers for this ECM. Our module is a compatible replacement for all of them.
What if this doesn’t fix my problem?
While this module fixes the common issues listed, proper vehicle diagnosis is key. We recommend confirming your diagnosis or consulting with a professional mechanic if you are unsure. A faulty ECM can mimic other failures, like bad wiring or a failing fuel pump.