3.6L V6 Engine Complete Assembly for 2018-2020 Cadillac CT6

A quick look at your own vehicle makes sure the right engine shows up:

• Check the 8th digit of your VIN to confirm it is 'S'.
• Verify the RPO Code 'LGX' on the Service Parts Identification label in the trunk.
• Confirm your drivetrain type (RWD vs. AWD) to prepare for oil pan and front differential transfer if AWD.
• Inspect your original engine's oil cooler setup to match the plumbing.

What the install really takes — plan and budget with confidence:

Special tools this job needs:

• GM Camshaft Holding Tool Set (EN-48313 / EN-49982 or equivalent)
• GM Flywheel Holder (EN-2342 or equivalent)
• High-Pressure Fuel Line Disconnect Tool
• Bi-directional Scan Tool

Budget for these consumables at install:

• Engine Oil: 6.0 quarts (5.7L) of GM Dexos1 Gen 3 approved 5W-30 full synthetic motor oil
• Oil Filter: ACDelco UPF63R (mandatory to prevent leaks/blowouts)
• Coolant: GM-approved Dex-Cool (50/50 pre-diluted)
• Spark Plugs: 6 new OEM ACDelco Iridium spark plugs
• Gaskets: Upper and lower intake manifold gaskets, exhaust flange/manifold gaskets, and thermostat housing gasket
• Front Differential Fluid (AWD models only): Fresh gear oil matching GM specifications
• Seals: Front and rear main seals (recommended preventative maintenance)

What your vehicle’s computers will need after the swap:

What’s involved: Crankshaft Position (CKP) Sensor Variation Relearn and Security Re-marriage

A crankshaft position (CKP) sensor relearn procedure is mandatory after installation for the engine to run correctly and not set a check engine light. Additionally, swapping the engine may require security re-marriage procedures to allow the car to start and run. A GM-compatible high-level scan tool (such as GM GDS2/Tech 2) is required.

Pro tips for a smooth first start-up — hand them to whoever does the install:

• The AWD Oil Pan Pass-Through: On AWD models, the right-side front axle intermediate shaft passes directly through a sealed tube cast into the engine's oil pan. Be extremely careful not to damage the inner shaft seals. You must transfer your original AWD oil pan and pickup tube to this replacement engine.
• Integrated Exhaust Manifold Threads: Exhaust manifolds are cast directly into the aluminum cylinder heads. Downpipe studs thread directly into the head and are highly prone to stripping if over-torqued. Always use a torque wrench.
• Active Fuel Management (AFM) Oil Passages: Dirt, debris, or old RTV silicone entering the oil passages can clog the AFM solenoids, leading to immediate lifter collapse or severe engine noise. Clean all mating surfaces meticulously.
• Torque-to-Yield (TTY) Fasteners: The harmonic balancer bolt, flywheel/flexplate bolts, cylinder head bolts, and subframe mounting bolts are single-use stretch bolts and MUST be replaced with brand-new OEM GM fasteners.
• Timing System Complexity: The LGX uses three separate timing chains with a complex two-stage timing procedure. If removing timing components, you must follow specific GM service information for Stage 1 or Stage 2 timing alignment.

Easy to get right once you know them:

• Ordering the Wrong Layout (Transverse vs. Longitudinal): Buying a 3.6L LGX engine pulled from a front-wheel-drive platform (like a Chevy Blazer or Cadillac XT5). The block casting and accessory mounts are completely different and will not bolt into a rear-wheel-drive CT6.
• Reusing a Contaminated Oil Cooler: Reusing an old oil cooler from a failed engine will wash trapped metal particles directly into the replacement engine, destroying it and voiding the warranty.
• Skipping the Crankshaft Relearn: Failing to perform the mandatory Crankshaft Position (CKP) Sensor Relearn using a bi-directional scan tool, leading to misfire codes and poor performance.
• Reusing High-Pressure Fuel Lines: Reusing the single-use metal high-pressure fuel lines is a major safety hazard that frequently results in high-pressure fuel leaks and engine bay fires.
• Using the Wrong Oil Filter: Using a standard PF63 filter instead of the mandatory high-pressure UPF63R filter, which can lead to gasket blowouts or leaks.
• Neglecting Oil Level: Low oil levels due to extended oil change intervals are the primary cause of premature timing chain wear.

Not issues with the units on this page — the manufacturer documented these for every engine of this family, wherever you buy one. Handy for your installer: