Q: We are having trouble with our 2012 Chevy Sonic. The key gets stuck and won't come out of the ignition. And now, the key won't turn the other way to be able to start the car. Sometimes just jiggling the steering wheel helps. While it was under warranty it was repaired and a sensor was replaced. Now the problem is back and it is not under warranty anymore.

A: My suggestion is to ask the dealership service manager to investigate whether this issue is a continuation of the original problem covered under warranty. Personally, I would hope it would be covered under the original warranty, or a customer "goodwill" policy.

The inability to turn the key to the start position may be related to a mechanical issue with the lock cylinder or a problem with the steering column lock mechanism, as illustrated by your intermittent success in "jiggling" the steering wheel. Flushing the lock cylinder with an aerosol electrical contact cleaner followed by a light application of a lubricant may help. Make sure the key is not bent or misshapen, causing the lock to bind. I've even read of folks lightly tapping the end of the key while it's in the ignition to help free any stuck tumblers.

Q: My 2006 Camry XLE with 97,000 miles has developed a "clunk" in the rear end when going over small or large bumps. A mechanic that I took it to told me that the rear struts are in good shape and do not need to be replaced. He does not have any ideas as to the source of the problem.

A: How about the strut mounts? My ALLDATA database pulled up Toyota service bulletin SU001-06 dated February 2006 addressing a thump noise from the rear suspension when traveling over bumps. Toyota issued updated rear upper supports and rear shock absorber service parts to fix this issue.

Did your mechanic check for possible contact between the exhaust system and the chassis? Any part of the exhaust system hitting the chassis when the car goes over a bump could create this type of noise.

Q: I have a 1999 Toyota Avalon with 132,000 miles that runs like the day I bought it. Recently, two lights on the dashboard came on; the check engine light and the traction control OFF light. The dealer said the EGR valve and an oxygen sensor need to be replaced for about $800. An independent shop said that the EGR should be replaced (occasionally the engine will stutter/vibrate), and that replacement of the EGR valve should also eliminate the traction-control OFF light from coming on. He also said that when you replace an oxygen sensor, there is a strong likelihood of it coming back on at a later date. I still love the car, but I don't think I want to put $800-$900 in a 16-year old car.

A: The only connection I can envision between the stutter/vibrate from too much exhaust gas recirculation (EGR valve) and the TCS shutting off would be a quick enough change in rotational speed of the front drive wheels relative to the rear wheels to mimic a problem with the system. But that's a huge stretch — I'm not sure I didn't create the mental picture just to fit the symptom!

Regardless, a scan tool should identify the EGR and TCS issues via specific fault codes. If the EGR is faulty, replace it and drive the car to confirm whether or not it was a factor in the TCS OFF issue.

You didn't mention whether the dealer identified a specific oxygen sensor fault code, but any vehicle with 132K miles on the original O2 sensor will benefit from a new one — better mileage and more efficient operation. As long as a new oxygen sensor is working properly, it should not trigger a fault code.