Car Doctor Q&A

Q I was recently reading about check engine lights, why they come on, common parts that fail and some diagnostics. With the complexity of systems that are integrated like a computer network can a car owner really do their own repairs today.

A Yes, you need to first start with a decent scan tool. A code reader will give you the code, but a true scan tool will allow you to read live data. A bi-directional scan tool will let you control some aspects of the car’s computer system. As an example, turning an evaporative emissions solenoid on and off, to see if it works. Scan tools do not have to be expensive, yes you can spend thousands, but you can also buy a decent scanner for less than $200. I have one from Innova that has served me well. In addition to a scan tool, you need to use all your human senses. So often I will see wiring issues, strong fuel, coolant, or oil smells all that can indicate a failed part and can turn on a check engine light.

Q On my five-year-old Ford F-150when using a voltmeter, I am getting 12.4 volts on the battery and 14.4volts on the alternator. Is this, okay? Should I be using something other than my digital voltmeter?

A Certainly, on the surface the number looks normal but, voltage is only part of the equation. The alternator can put out 130 amps of power. The reading of 12.4 volts on the battery indicates about 80 percent state of charge. What is important with a battery is capacity. All batteries have a cold cranking rating (CCA). As important as it is to check voltage, checking CCA is important to check the health of the battery. I recently was using a pretty inexpensive (less than $70) battery tester from a company that I had never heard of called Topdon. Although the readings are not compensated for temperature, initial results reading, voltage, cold cranking amperage, starter and alternator testing are pretty good.

Q I have a 2006Chevy Impala SS, and the headlights will not shut off. Even If I turn off the “automatic lights” switch they stay on. My mechanic has no idea. We researched a little bit, and some forums say that there is a relay or module that is inside of the fuse box and is not serviceable. The problem is you need to replace the entire fuse box and it is discontinued. How can the problem be tested, other than me buying a used fuse box, changing it out, and hoping for the best? Right now, I pulled all the fuses out, so it does not drain my battery.

A Looking at the wiring diagram the low and high beams run on different relays, but everything runs through the headlight switch. Before I condemned the fuse box I would test the switch. If it does turn out to be a module perhaps you can rebuild it. This year I had a technician on my radio program from www.upfix.com. This company fixes a variety of electrical components. Rather than try a used part you could take out the part from your car and send it to them for testing and repair.

Q Recently while driving my 2012 Honda CRV with 84,000 miles, I have noticed a slight shimmy while driving on the highway going 65-70 miles per hour and I am about to take a trip to Florida. Could it be as simple as making sure my tires are inflated properly or do I need a tire rotation? Should I have my mechanic look deeper? A I would have the tires looked at and rebalanced. An out of balanced tire or possible damaged tire or wheel

will cause a shimmy at highway speeds. When balancing the tires the technician can inspect the tires for any possible damage. If I were driving 1500 miles, I would want to know my vehicle tires are perfect.

My 2022 Honda Accord Touring Hybrid with 19,000 miles has a noise issue with the brakes. I have been told it is from their use of metal in the brake pads and heard this from two different Honda dealers. Living near the bay, the salt air does not take

long for the rotors to get a quick coating of rust and then the noise starts. Does Honda have any solution for this? And are the brakes even quicker to need replacement because of the rusting issue? The noise is only heard when the car is in reverse even before brakes are applied. Other than that, the car is great.

I drive a lot of new cars and on some vehicles the rotors get a light coating of rust overnight and on others not at all. The rust is typically just surface rust and “wipes” off after a few light stops. This rusting should not have

any effect on the longevity of the brakes. I also looked and Honda has not issued any bulletins for an updated part. I would consider the surface rust normal.

My daughters 2014 Smart for 2 Passion has a P0949 code which I understand is a learning code. It has been driven well over 100 miles since code first appeared. I read your advice on a 2018 Chevy Cruz and was wondering if some certain trip would erase the code? This code if for transmission and will typically come up if the battery is disconnected. If it does not relearn in the normal procedure, try

moving the gear selector lever to park position P. Turn off the engine, wait at least 30 seconds before restarting. Press the brake pedal, restart the engine. Three bars instead of P appear in the multifunction display. Wait at least 30 seconds and the P should reappear. If that does not happen it could be the sensor, the engine may be running a bit rough or a wiring issue. Depending on what is found your mechanic may be able do a relearn with a scan tool.