Q: Please help! Neither my local Mazda dealer nor independents can come up with a solution to the problem with my 2006 Mazda Tribute. Not always, but every so often, the remote will not lock the doors, will not unlock the doors, and then I cannot start the car. After much manipulation of the remote, open and closing doors, etc., it finally works. I have purchased new remotes, changed batteries in remotes, but nothing helps. Sure hope you can help; it is mighty frustrating.

A: Did either service agency plug in a scan tool to check for fault codes? If not, this is the first step. A search of my ALLDATA automotive database found that if codes B1300 or B2111 are stored in memory the problem is with the power door lock circuits, possibly a short to ground. B2425 would indicate that the RKE — remote keyless entry — transmitter is out of sync with the smart junction box (SJB). This can occur if the RKE button is pushed a number of times when outside the range of the transmitter. To resynchronize the rolling code system, with the key off press any button on the RKE four times within 30 seconds. The SJB and/or its connections might be at fault.

When the vehicle will not start, do you notice the security warning light on the dash? The PATS — passive anti-theft system — on this vehicle has an anti-scan feature that prevents attempts to enter or start the vehicle with some type of rolling code generator. If a damaged, uncoded or incorrect key is used to switch the ignition on, the PATS system will prevent the vehicle from starting and flash the security light rapidly for 60 seconds, then flash a fault code. If you have two keys, switch the ignition off after the security light has flashed rapidly for 20 seconds, remove the key and insert the other key. Turn the ignition on, then off, then try to start the car. If it starts, the first key was not programmed properly.

Q: My 2010 Buick LaCrosse intermittently will not shift from Park to Reverse. The shift is on the console. The dealer says he has no clue as to how to fix this. GM, via online computer conversation, had no clues. I am now preventing this problem by always placing the car's parking brake on before taking my foot off the brake to turn the car off. What is going on?

A: The most likely cause, and one the dealer should have investigated, is a problem with the shift lock solenoid located in the shift console. This safety system is designed to prevent the vehicle from starting unless the shifter is in Park and the driver's foot is on the brake pedal. Here's how it works: With the ignition switch on and the foot brake applied, the BCM — body control module — supplies voltage to the permanently grounded shift lock solenoid. The solenoid actuates, unlocking the shift lever to allow you to shift out of Park.

So, it would seem logical that either the brake pedal switch is not telling the BCM that your foot is on the brake pedal during an attempted start, or the BCM voltage signal to the shift lock solenoid is failing to reach or activate the solenoid.

Q: I read your comment that you change oil more frequently than recommended by the manufacturer. Why? Isn't it wasteful to change oil more often, wasting both money and oil? On what do you base your recommendation?

A: Simple answer: it's MY vehicle, not the manufacturer's. The cost of this "extra" maintenance is far, far less than the cost of premature engine problems due to sludge from lubricant oxidation, contamination, fuel dilution or additive depletion. Are any of these likely to happen? No. Do they happen? Yes. Who pays for repairs, lost value, etc.? Carmakers? No. Me? Yes.

And the "prematurely" changed oil is not wasted, it is recycled. In fact, I often re-use it in my small-engine equipment.