Question: The "service engine soon" light in my 2002 Saturn SC2 with 61,000 miles keeps turning on even though I've had the vehicle checked several times. At present, the light is on constantly. A technician I spoke with said this probably means there's a tiny leak of gasoline vapor somewhere, which will not be destructive to the car. What do you think should be done?

Answer: Fix it. A simple scan of the powertrain control module should identify the specific diagnostic trouble code that is triggering the light. A number of auto-parts stores will provide this service at no charge.

Since 1996, carmakers have been required to monitor the evaporative emissions control system for any leaks and for whether the purge-and-vent solenoids are opening and closing properly.

One of the most common causes for an EVAP fault code is a gas cap that does not seal properly.

Q: My question is regarding the daytime running lights becoming so popular on new cars. Why do the car manufacturers have the turn signal cancel out these lights during the day? I see it frequently when a car is approaching with daytime running lights on. The car activates the right-turn signal, and the right headlight goes out. Why is it programmed this way?

A: Interesting question. Daytime running lights were developed to improve visibility of vehicles to nearby motorists and pedestrians.

With the increased intensity of modern headlights, the relatively low-intensity turn-signal lamps on the front of vehicles can be obscured by very bright high-intensity discharge headlights. To make sure the turn signal on the front of the car is visible, several carmakers program their vehicles' lighting system to cancel the daytime running lights on that side when the turn signal is engaged.

Remember the adage "Solve one problem, create another"?

Q: My wife purchased a new 2015 Volvo XC60 in 2014. It now has 25,000 miles on the odometer.

I noticed the rear end was grinding whenever a right or left turn was made after a complete stop. It seemed more pronounced during right turns. The dealer could not duplicate the condition and suggested that whatever I was hearing or feeling was likely due to all four tires being "cupped." The service manager told me not to worry since we had another year and about 2,000 miles of warranty remaining. Now it seems to be getting worse. What to do?

A: Grinding noises while turning are often a symptom of a hub-wheel bearing issue. When turning, the ball bearing tends to lean against the side of the bearing race. Wear or corrosion on this surface of the race is what creates the roughness or noise.

Sometimes you can actually feel this roughness when, with the suspension on a jack stand, you place your hand on the coil spring above the tire and spin the wheel by hand.

An automotive database pulled up Volvo bulletin TJ25167, which lists a replacement hub incorporating a new splash shield to improve bearing life. Next time you take the car to the dealer, suggest that a technician drive with you to experience the noise.

Paul Brand, author of "How to Repair Your Car," is an automotive troubleshooter, driving instructor, and former race-car driver. paulbrand@startribune.com.