2017 Buick Lacrosse

The 9T50 (Hydra-Matic 9T50) nine-speed automatic transmission exhibits harsh and erratic shifting, particularly during low-speed driving. Owners report clunking when shifting from Park to Drive or Reverse, delayed upshifts, and a noticeable lurch between 1st and 2nd gear. The transmission may also hunt between gears while cruising on slightly hilly terrain.

Dealer performs a TCM (Transmission Control Module) software reflash with the latest calibration, which GM has updated multiple times. If shifting issues persist, the valve body or internal solenoid pack may need replacement. Reference GM TSB 18-NA-284 for 9-speed transmission shift quality improvements. A complete transmission fluid exchange may also improve shift quality.

The StabiliTrak and traction control warning lights illuminate intermittently, sometimes accompanied by a 'Service StabiliTrak' message. When the warnings activate, the system may reduce engine power unexpectedly, even on dry pavement. The issue is often caused by a faulty steering angle sensor, wheel speed sensor, or a software glitch in the electronic stability control module.

Dealer diagnoses the specific fault code stored in the EBCM (Electronic Brake Control Module). Common fixes include replacing a faulty wheel speed sensor, cleaning or replacing the steering angle sensor, or reprogramming the EBCM. Reference GM TSB 15-NA-113 for StabiliTrak warning diagnosis. Ensure all four tires are the same size and properly inflated.

LaCrosse models equipped with the optional Continuously Variable Real-Time Damping (CVRTD) suspension develop leaking rear shock absorbers and, on models with rear air leveling, the air springs lose pressure overnight causing the rear to sag. Standard shock-equipped models also experience premature rear shock wear, resulting in a bouncy ride and poor handling.

Replace the rear shock absorbers with OEM or quality aftermarket units. For models with air leveling, replace the air springs and inspect the compressor and lines for leaks. Some owners convert from air suspension to conventional coil springs and shocks to eliminate future air system failures.

The Buick IntelliLink infotainment system with the 8-inch touchscreen freezes during use, exhibits significant input lag, and occasionally reboots while driving. Bluetooth audio drops out, navigation destinations take excessive time to calculate, and the system may fail to pair with phones after a software update. Some owners report the screen going completely black and requiring a vehicle restart to recover.

Dealer performs an infotainment system software update. A master reset of the infotainment system (through the settings menu) may resolve software corruption. If freezing persists after updates, the infotainment control module may need replacement. Ensure USB cable connections are secure, as a loose cable can cause CarPlay/Android Auto disconnections.

The 3.6L LGX V6 engine can consume oil between changes, with some owners reporting a quart consumed every 2,000-3,000 miles. The piston rings may not seat properly, allowing oil to pass into the combustion chamber. Symptoms include low oil level warnings between scheduled oil changes, blue tinge to the exhaust smoke, and fouled spark plugs.

Monitor oil level frequently and top off as needed. GM considers oil consumption of up to 1 quart per 2,000 miles within normal parameters for this engine. If consumption exceeds that threshold, an oil consumption test may be performed under warranty. Severe cases may require piston ring replacement, which involves removing the engine for disassembly.