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Q: I have a 2010 Infiniti EX35. Last December my engine light went on and I had the codes checked at AutoZone — P0014 and P0024. Mechanics said it was due to dirty oil. They reset the code but it came back on in five miles. I had a synthetic oil change and a mechanic told me to run SeaFoam through it and run it 50 miles prior to the oil change. A local garage and Infiniti dealer said I needed to have two modules replaced for $2,600. They also stated that this may not fix the problem as the system could be compromised with existing sludge in the motor. The car runs fine, mileage and performance are fine. My question is what's the harm in running it without the fix? Can I run the car until it starts to degrade in performance and then bring it in? What is your advice?

A: Are the P0014 and P0024 the only diagnostic codes found? ALLDATA shows these two codes refer to a problem with the EVT — electronic valve timing — on both banks of cylinders. Additional DTCs could have pinpointed the crankshaft position sensor (P0035), cam position sensor (P0340), exhaust valve timing control sensor (P1078), exhaust valve magnet retarder, the exhaust valve timing control pulley assembly or the timing chain and gears.

If P0014/P0024 are the only codes, sludge or debris accumulating on the camshaft's pickup might be the problem — thus the suggestions of adding SeaFoam and a couple of short interval oil and filter changes are the simplest and least expensive first steps. I'd hesitate to replace expensive modules without specific DTCs confirming a problem.

Q: I have a 2002 BMW Z3 with the 2.5-liter engine. The battery was dying so I went to my local shop and had it replaced. When I went to turn on the radio, I saw a message saying that I needed to enter a security code. I was told that the code would be in the owner's manual that came with the vehicle. I found it and tried repeatedly to activate the radio without success. The shop also tried using the code in the owner's manual as well as going online to see if another code was available. No luck.

A local BMW dealer was also unsuccessful. I finally gave up and purchased a replacement from a local electronics shop. I still have the original radio in my garage and whenever I see it, it grinds my gears. Is there some way that you can find to get this thing to work?

A: Like you I'd find this a compelling challenge. You could try powering it up on your bench with a 12-volt battery, but it may require the unit to be installed in the vehicle before entering the security code.

With that said, there are a couple of things you could try that may have been overlooked. After three unsuccessful attempts at entering the code, BMW radios lock out any additional attempts until the ignition and radio have been left on for one hour. Also, some BMW radios require pushing the right arrow key after entering the code before the unit will function.

Finally, did you purchase the vehicle new or used? Is that the original radio for the car? If not, your only hope would be to identify the proper code for the replacement radio through BMW.

Q: I have a 2005 Dodge Grand Caravan with 148,000 miles on it. Recently the dash and headlights started to flicker intermittently. The battery is new and I'm suspecting an alternator problem. Any thoughts?

A: Is the new battery rated for this vehicle? Are the cables clean and tight? Does the battery light indicate low voltage when the flickering occurs? A scan tool may identify a charging problem, but I'd suspect something like the high/low beam switch on the tilt steering column or a poor lighting system ground.