Q: My 2013 Charger R/T has a recurrent issue with the "Check engine" light. I was advised to open and close the gas tank door as a recent fueling may have caused the issue. It went away about two starts later. It was on again, off again with limited frequency. I had the dealership check the vehicle, as it disables the remote start and Eco Drive whenever it occurs. To date they have been unable to identify any stored code or issue. They downloaded new software and said that may have been the cause. I'm at a loss, I'm now out of warranty and the problem seems to be more recurrent now. Any ideas or guidance would be appreciated.
A: The most likely explanation is a small leak in the evaporative emissions control system (EVAP). To prevent fuel vapors from reaching the atmosphere, the PCM monitors the sealed fuel tank under certain conditions and triggers the P0456 DTC fault code if it detects a change greater than spec. However, if the PCM sees three start cycles without noting the fault, the code is cleared. Perhaps that's why the dealership hasn't found a stored DTC.
The dealer's scan tool can perform an ESIM (Evaporative System Integrity Monitor) "forced monitor" test at room temperature to see if the DTC will be triggered. The dealer can also verify and detect an EVAP leak with a special air/smoke test.
Even though your vehicle may be beyond the two-year/24,000-mile basic emissions warranty — the catalytic converter and PCM are covered for eight-year/80,000 miles — I would hope that the fact that you had the issue addressed during the original warranty period would encourage the dealer to resolve the issue without cost to you.
Q: I own a 2011 Toyota RAV4 V6 all-wheel-drive with 59,000 miles. I have pulled a boat and trailer for approximately 2,500 miles since the car was new. At my last oil change the dealer recommended replacing the front and rear differential oil. According to the maintenance book, this service is recommended every 15,000 miles if the vehicle is frequently used for towing. Replacing the transmission fluid at 60,000 miles is also recommended if the same driving conditions exist. This is the first time they have brought up servicing the differentials and they didn't say anything about replacing the transmission fluid.
I am not convinced this service is needed and I think the estimate of $73 for each differential is outrageous. Am I being penny-wise and pound-foolish, or should I go ahead and have the work done?
A: One part of Toyota's "severe service" operation guideline is towing a trailer. It does not specify how many miles of towing qualify for "severe service," but does indicate that if you use the vehicle for towing "only occasionally," you do not need to follow "severe service" guidelines. Still, as I have always said, it is your vehicle — not Toyota's. Thus, it's up to you to make the maintenance decisions.
Even though only roughly 4% of the vehicle's mileage is involved with towing, I'd be inclined to change the fluid in both diffs, transfer case and transmission. This would need to be done only once, maybe twice, in the vehicle's service life — a rather small percentage of the total cost of owning and operating the vehicle. And you might want to check the cost of these services at independent shops. As long as the correct lubricants are used, you may find significant savings.
Q: You recently answered a question regarding tire pressure. You referred to different tire pressure gauges. We all know that if you checked one tire with five tire pressure gauges you will have five different readings! What do you recommend as a certification for our tire pressure gauges?
A: The simple answer is to buy two digital electronic pressure gauges. If they register significantly different pressures on the same tire — which is very unlikely — split the difference. That's close enough.