I have 125,000 miles on my car and kept up with all maintenance. Now there is a transmission issue with the computer reading failed to downshift to lower gear. And there is a humming noise after warmup.
Greetings. The humming noise is likely caused by a faulty PCV valve or oil trap hose. The engine of the vehicle produces a lot of suction and the PCV valve and hose is made to regulate some of the suction by the opening and closing of the valve. The PCV valve commonly becomes stuck open in old age after warming up,which will allow too much air suction. The suction usually can be heard as a humming or whistling noise. The Volvo dealers are aware of the issue and have extended warranties on those parts. I suggest calling your local Volvo dealership and ask them about the warranty of that part on your vehicle. If it is under warranty they will replace it free. Regarding the transmission issue there is a software update available from the dealership that addresses hard shifting and no downshifting. A simple reprogramming will likely fix your problem. If it doesn't and the transmission still has issues I suggest checking, then changing the fluid if necessary. 80 percent of all transmission failures stem from a fluid related issue.(lack of fluid or old fluid)
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