2018 Chevrolet Impala: What to check before buying

Transmissions slip, shudder, skip gears and shift hard, most often around the lower gears. Some cars buck in stop-and-go traffic, get stuck in gear, or will not accelerate at speed. That creates a real risk of being hit from behind on the highway. Warning lights often come on only after the failure, or not at all. Dealers often decide the whole transmission needs replacing, and bills run into the thousands. One owner reports hard shifts returning after the replacement. Failures cluster between about 65,000 and 98,000 miles.

Power cuts out without warning. In some reports the interior and exterior lights go dark while driving. Other cars only click when you try to start them, or the driver information display goes blank. After a long drive, auto stop can shut the whole car off at a light, and it needs a full restart. One owner was told the battery fuse block was to blame. Battery replacements do not always fix it. Other reports describe tire pressure sensors that stop reporting and a corroded side detection sensor. Drivers who hit the start button at highway speed lose the engine and lights at once.

Power steering assist cuts out suddenly. The wheel goes stiff and the car is hard to keep in its lane. Some drivers see a "Power Steering, Drive With Care" or service power steering message. Others get no warning at all. Failures happen while driving or when backing out of a parking space. Dealers usually trace it to the electric power steering motor or the steering gear and call the repair expensive. Reported mileages run from 26,473 to about 74,000, so even low-mileage cars are affected.

The passenger seat airbag sensor malfunctions. The airbag warning light comes on with chimes and an OnStar alert, and it returns after being dismissed. Dealers diagnose the passenger seat airbag module and sensor, and owners near 62,000 miles were told the repair falls outside warranty. In one crash with a deer, the airbags did not deploy and the driver was injured. In another report, the driver's airbag went off overnight in a parked car after its warning light had been on.

All four reports describe a crash where the brakes did not stop the car. Drivers slide into the car ahead at freeway speed, at low speed, or pulling out of a lot. One car kept rolling in reverse and then forward even with heavy pedal pressure, and it ended up hitting a signpost. Several drivers say stops felt long or weak for months before the crash. One crash caused an injury.

Water and condensation collect inside both headlight housings, sometimes pooling at the bottom, and the headlights get noticeably dimmer at night. One dealer proposed drilling drain holes in each housing instead of replacing them. One owner faces about $200 to replace both lights. The one dated report puts the problem at about 44,000 miles. A separate crash report describes a rear-end collision but does not tie it to a lighting fault.

Power drops suddenly at highway speed and a Reduced Engine Power warning appears, which raises the risk of being rear-ended. Restarting the engine brings power back, but the check engine light stays on and the problem keeps coming back. The other report describes a strange odor in the cabin that a dealer traced to a leaking AC evaporator coil, the same failure many owners file under other categories. That coil was replaced at 39,000 miles.