Car Doctor: Why does my Jetta's steering lock when I'm backing up?

After this happens, you stop, put the car in park, shut it off and restart it, and all is fine until it does it again in about two weeks.

We took it to a VW-certified dealer, who couldn't find any error codes and spent time trying to unsuccessfully re-create the condition. It is a safety concern, and we appreciate any advice you have.

A: This model, like many Volkswagens, uses a key lock and an electronic steering wheel lock module. I suspect the lock module has an intermittent fault that allows the engine to start but doesn't let the steering unlock.

There doesn't appear to be an easy method to diagnose this, if it is a module or wiring fault.

I would go back to the Volkswagen dealer and have them check the module. Also, report the issue to nhtsa.gov/report-a-safety-problem.

Q: I just purchased a 2008 Saturn Outlook. The sellers said it wouldn't charge the battery and they tried two alternators and batteries. So, I thought it was an easy fix of a fuse or poor ground. That was a month ago.

I learned that the charging system is controlled by the computer. I've checked grounds and changed fuses, as well as the battery current sensor and belt with tensioner. Still, the alternator doesn't charge.

What do you think? Is it a bad computer, or is there something else? I did order a GM Tech II scan tool, which might help me.

A: It sounds like you have done most of the work with power and grounds, such as making sure the alternator is grounded. The charging signal is sent to the ECM (engine control module) and BCM (body control module) and, based on the signal, will determine how the alternator charges. Like most ECM control devices, it uses a 5-volt reference signal.

Although it certainly could be a faulty computer, most problems are traced back to broken/corroded wiring. Having a dedicated GM scan tool (even an outdated one like a TECH II) would be helpful for checking for both charging system and battery codes.

Q: I have a 2007 Buick Lacrosse. Every time I get an oil change, I choose the synthetic oil. Is that really necessary? Or can I switch to regular oil without any issues?

A: As long as you use the General Motors recommended Dexos, you are fine. On the other hand, synthetic oil is better than regular oil, reduces wear and allows easier starting during cold weather.

Q: I only have snow tires in the front on my front-wheel-drive Toyota Corolla SE. Snow tires are expensive, so I am trying to get by with just front snows. I have been told I should have four snow tires.

If I drive too fast around corners, I tend to fishtail in the snow. Is there anything I can do?

A: It is best practice to have four tires that match.

Putting snow/winter tires on the front of a front-wheel-drive car may get you moving in the snow, but braking will suffer. My suggestion is to get two more snow tires and an extra set of wheels. This way, at least, the winter switchover of tires will be less expensive. Also, by using your winter tires, you will get longer life out of your summer tires.

John Paul is the AAA Northeast Car Doctor. He has more than 40 years of experience in the automobile industry and is an ASE-Certified Master Technician. Write to John Paul, The Car Doctor, at 110 Royal Little Drive, Providence, RI 02904. Or email [email protected] and put "Car Doctor" in the subject field. Follow him on Twitter @johnfpaul or on Facebook.