My SUV’s automatic rain sensor is all wet 

Cars

John Paul, AAA Northeast’s Car Doctor, answers a question from a reader who’s having no luck with his new vehicle’s rain-sensing system.

Q. I recently purchased a 2022 Hyundai Tucson which was equipped with an automatic rain sensor to control the wipers when raining. It has never worked from the start, and after three frustrating visits back to Hyundai for service we’re back at square one with no resolution to the problem. Any thoughts or ideas on the issue?

A. As long as the wipers are in the “auto” setting they should come on whenever the windshield gets wet. Spraying the windshield with a light spray of water should be an easy method to verify whether the system works. At this point I would ask the dealer to bring in a field engineer to look at the problem. 

Q. I have a 2003 Toyota Tacoma 2.4L pickup with 110,000 miles. The check engine light is on with code PO171 .  I’ve watched YouTube videos on the code and have been unable to correct the wacky (high) fuel trims.  I checked for vacuum leaks in the EVAP system and brake booster.  The engine vac at idle is about 20. I disconnected the vacuum lines for the EVAP system and brake booster and cleaned the MAP sensor with no change. I’ve checked many other things, but have had no luck. I’m reluctant to take it to a shop since the cost to diagnose and repair could approach the value of the truck.  

A. The most common fixes are replacing the O2 sensors followed by replacing the mass air flow sensor. I wouldn’t think it is a fuel pressure or volume issue based on how you say it runs. I’m also guessing there are no exhaust leaks. One odd one that I have seen is a PCV valve and hose causing the issue. In repair history there are a few cases of faulty ECMs, which is certainly possible but in general very unlikely. One final tip, be a bit weary of some aftermarket oxygen sensors, I have seen some that just don’t work. 

Q. I was wondering why you do not emphasize ASE-certified mechanics when recommending a shop. AAA, of course, is fine, however, you are ASE certified and I would believe this helps someone to know he can trust that his mechanic is well trained. I have a lot of respect for training, and the ASE testing is tough.

A. Thanks for the reminder about ASE certification. At AAA, to become an Approved Auto Repair shop we require ASE certification, and frankly I’m used to AAA AAR shops being ASE certified (which we check on an ongoing basis). Yes, if you are in an unfamiliar area, looking for AAA Approved Auto Repair signs. ASE signs are a good place to start when looking for a repair shop. 

Q. Are OEM filters the best for general use of cars? One can assume that the manufacturer’s engineers have developed the filters to best protect their vehicles. Are aftermarket brands better assuming cost is not in the equation? I have a Chevy. Should I use a Delco oil filter or a Hastings oil filter? 

A. You can never go wrong with using factory OEM filters. You mentioned Delco and Hasting, and both are great filters. Since Delco filters are readily available, if I had a GM vehicle, that is what I would use. On my family vehicles I use the factory filters or try to find the supplier who makes the OEM filter. 

Q. My wife’s 2012 Lexus RX 350 has a battery that is at least three years old. Recently, a repair shop ran a test, and claimed it was at 40 percent capacity. There are no obvious indications that it is getting weaker.  At what point would you replace it and where would you go, the dealer, tire store, or auto parts store? 

A. If it is at 40 percent capacity, it is time to replace it before the temperatures really drop. At freezing temperatures, a good battery can lose up to a third of its cranking power, and when the temperatures drop to zero the engine can take up to 50 percent more power to crank due to the thicker oil and engine tolerances. As you are checking battery prices, AAA members (if you are one) can have a quality six-year Interstate battery delivered and installed at your home for a competitive price. Prior to installation AAA technicians also test the electrical system and double check the current battery’s performance. 

John Paul is AAA Northeast’s Car Doctor. He has over 40 years of experience in the automotive business and is an ASE-certified master technician. E-mail your car question to [email protected] Listen to the Car Doctor podcast at johnfpaul.podbean.com.