2004 XC70 Low Power
 

Hi, I have an unusual problem that the shop has not been able to track down. It is not a fatal problem, but it is quite frustrating. Gradually the car has less and less power. But if I disconnect the battery it temporarily comes back

I have no DTCs (when I checked recently). The dealer reportedly checked the turbos and boost pressure and said they were fine. I have had various computer upgrades including the transmission

I drive 50 miles each way to work, a part of the drive over a 1500 foot climb in 6 miles.

If I disconnect the battery for a minute or so, the power comes back. First day after disconnecting the battery I get good power going up and over the hill even if held in 5th, by the third or fourth day it is down shifting too much, and if held in 5th, feels like it has no power.

Because the power comes back when I disconnect the battery, it leads me to believe that a sensor is bad or marginal and it gradually gets relearned by the computer.

Any thoughts about what to look at would be great -- I don't want to take it to the shop because it winds up being trial and error and I already have 125K miles

Thanks,
Gary