Is Your 6.6L Duramax Acting Up? Get Back in Command.
If you’re dealing with a no-start condition, erratic engine behavior, or a persistent Check Engine Light on your GM heavy-duty truck or van, a failing Engine Control Module (ECM) is often the culprit. As the brain of your vehicle’s powertrain, when the ECM falters, everything from fuel delivery to transmission communication can be affected. This isn’t just an annoyance; it’s a critical failure that sidelines your workhorse. This fully tested, used ECM, part number 12654088, is the reliable and cost-effective solution to get your truck back on the road and running strong.
The Smart Solution: Programmed Specifically for Your Truck
Don’t waste time and money on a blank module that requires an expensive trip to the dealership for programming. We handle the critical first step for you. Before we ship your part, our technicians will flash this ECM with the latest official GM software calibrations, precisely matched to your truck’s Vehicle Identification Number (VIN). This ensures that when the module arrives, it’s ready to communicate with your vehicle’s specific systems and options. You just provide your VIN at checkout, and we take care of the rest.
Expert Pro Tip: Understanding the Security Relearn
Over my 20+ years in diagnostics, the most common call I get after an ECM replacement is, “My truck cranks but won’t start!” In 99% of these cases, the replacement ECM is working perfectly, but the vehicle’s anti-theft system has locked the engine out as a security measure. This is normal. A simple “Security Relearn” or “Vehicle Theft Deterrent (VTD) Relearn” procedure using a capable scan tool or GM’s TIS2Web software is required to sync the new ECM to your truck’s keys and BCM. It’s a standard final step for this repair, so don’t be alarmed if it’s needed.
Is This the Right Part for Your 2013-2014 Sierra 3500 ECM?
A faulty engine computer can manifest in numerous ways. I’ve seen these exact modules cause symptoms that mechanics sometimes misdiagnose, leading to wasted money on unneeded parts. Check if your truck is experiencing any of the following:
- โ Complete no-start or intermittent starting issues
- โ Check Engine Light is on with communication-related fault codes (U-codes)
- โ Poor fuel economy or noticeable loss of power
- โ Harsh or incorrect shifting patterns
- โ Problems with emissions systems like the DPF or DEF
- โ Unexplained stalling while driving
Installation Guide & Post-Install Procedures
Replacing the ECM on these trucks is straightforward. It’s typically located in the front, left-hand (driver’s side) of the engine compartment.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery or batteries before starting any electrical work.
- Locate the ECM: Find the module on the driver’s side of the engine bay.
- Disconnect Connectors: Carefully release the locking tabs and unplug the large electrical connectors. Inspect the pins on both the harness and the new module for any corrosion or damage. Clean them with electrical contact cleaner if necessary.
- Remove the Old ECM: Unbolt the old module from its mounting bracket.
- Install the New ECM: Mount your new, pre-programmed ECM and securely reconnect the electrical harnesses. You should hear a distinct click as they lock into place.
- Reconnect Battery: Reattach the negative battery terminal.
- Final Steps: Turn the key to the ‘ON’ position. If the vehicle starts and runs normally, you’re all set. If it cranks but does not start, the Security Relearn procedure mentioned in our Pro Tip must be performed by a qualified technician. Other procedures, like a Crankshaft Position Variation Relearn or Injector Flow Rate programming, may also be necessary depending on your vehicle’s specific stored codes and symptoms.
Guaranteed Fitment
This ECM is a direct replacement for service numbers 12654088 and 12653319. It is compatible with the following GM vehicles equipped with the 6.6L Duramax diesel engine:
- 2013-2014 Chevrolet Silverado 2500 / 3500
- 2013-2014 GMC Sierra 2500 / 3500 (including Denali)
- 2013-2014 Chevrolet Express 2500 / 3500 Van
- 2013-2014 GMC Savana 2500 / 3500 Van
Please verify the part number on your original module to ensure a perfect match.