Is Your Cadillac XTS Running Rough? The ECM Might Be the Culprit.
If you’re experiencing frustrating issues like a persistent Check Engine Light, poor fuel economy, engine stalling, or a no-start condition in your 2017-2019 Cadillac XTS, the problem may lie deep within its electronic nervous system: the Engine Control Module (ECM). The ECM is the master computer responsible for managing everything from fuel injection and ignition timing to emissions controls and transmission shifting. When it fails, the entire vehicle’s performance and reliability are compromised.
From the Diagnostic Bay
I once had a 2017 Impala with the 3.6L V6 come into the shop with a bizarre, intermittent stalling issue that no one could figure out. It threw a dozen different codes, from misfires to communication errors, leading other technicians down rabbit holes of replacing sensors and coils. After hours of diagnostics, I traced the issue back to a failing ECM that was corrupting data on the CAN bus network. The module wasn’t completely dead, but it was causing chaos. Replacing it with a correctly programmed unit, like this one, solved every single issue instantly. It’s a powerful reminder that the ECM is the true brain of the operation, and when it’s not healthy, nothing else works right.
Common Symptoms of a Failing ECM
A faulty engine computer can manifest in numerous ways. If your Cadillac XTS is showing any of these signs, it’s time to consider a replacement 2017-2019 XTS ECM.
- ✔ Persistent Check Engine Light (CEL) that won’t clear or returns immediately.
- ✔ Unexplained drop in fuel efficiency.
- ✔ Engine misfires, stumbling, or hesitation during acceleration.
- ✔ Intermittent or complete failure to start the engine.
- ✔ Rough or erratic idling.
- ✔ Automatic transmission shifting problems or harsh shifts.
- ✔ Communication errors with diagnostic scan tools.
- ✔ Failure to pass state emissions testing.
The Direct-Fit, Programmed Solution: Part Number 12666070
Don’t let a faulty computer keep your luxury sedan off the road. This Engine Control Module, part number 12666070, is the definitive solution for your vehicle. We take the guesswork and hassle out of the repair by pre-programming the module specifically for your car. When you place your order, simply provide us with your vehicle’s 17-digit Vehicle Identification Number (VIN). Our technicians will then flash the module with the latest, most stable software updates directly from GM. This ensures that the computer is a perfect match for your vehicle’s specific configuration, options, and emissions standards.
This plug-and-play approach saves you a costly trip to the dealership and eliminates the need for expensive proprietary scan tools for programming. The module arrives at your door ready for installation, getting you back on the road faster.
Cross-Reference Part Numbers:
This module is a direct replacement for the following GM part numbers: 12667002, 12666070, and 12667189. You can have complete confidence in its compatibility and function.
Verified Vehicle Fitment:
This ECM is guaranteed to fit the following vehicles and configurations:
- Cadillac XTS: 2017-2019 (3.6L, VIN 3 – 8th digit, opt LFX)
- Chevrolet Impala: 2017-2019
- Chevrolet Traverse: 2017
- Chevrolet Equinox: 2017
- Chevrolet Caprice: 2017 (3.6L)
- GMC Acadia: 2017 (Limited, VIN J – 11th digit)
- GMC Terrain: 2017
- Buick Enclave: 2017
- Buick Regal: 2017
- Buick Verano: 2017
Frequently Asked Questions
What is an ECM and what does it do?
The ECM, or Engine Control Module, is your vehicle’s main computer. It controls and monitors the engine’s performance, fuel delivery, ignition timing, emissions systems, and communicates with other vehicle modules to ensure everything operates smoothly.
Is this 2017-2019 XTS ECM ready to install?
Yes! This module is sold as a pre-programmed service. You must provide your vehicle’s VIN at the time of purchase. We will flash the unit with the correct GM software for your specific vehicle before shipping it. This makes installation much simpler.
Where do I find my VIN?
Your 17-digit Vehicle Identification Number (VIN) can be found on a metal tag on the driver’s side of the dashboard (visible through the windshield), on the driver’s side door jamb sticker, or on your vehicle’s registration and insurance documents.
Will I need to do anything after installation?
In many cases, the module is a direct plug-and-play installation. However, some GM vehicles may require a simple ‘Security Relearn’ or ‘Crankshaft Position Variation Relearn’ procedure after installation. These can often be performed without special tools and instructions are widely available online.
How do I know for sure my original ECM is bad?
While the symptoms listed are strong indicators, a definitive diagnosis should be made by a qualified technician. This involves checking for power and ground at the ECM, testing communication networks, and ruling out other potential causes like wiring or sensor faults.