pathfinder 98 SE transmission erratic

[shahabc]

I have pathfinder SE 98 with 62,000 miles. For last few months, I have noticed that at higher speeds 50-60 mph, sometimes, the transmission downshifts (thus raising the rpms significantly). It happens around 15% of the time. Sometimes does not do this at all. Over the months, the problem has not increased. I am confused. My usual mechanic can't tell me anything.

[KoukiS14]

Welcome to NICO!!!This problem may be the result of a faulty TPS (throttle position sensor). If there's any fluctuation in voltage, it could cause a drop out of overdrive.

If you're inclined to do so, you may test the voltage with a multimeter... or bring it in and have this test performed.

[KoukiS14]

Could ALSO be a fault VSS (vehicle speed sensor)Personally, I'd lean more toward TPS

For reference, here is the code for a bad VSS from the FAQ listed in the Pathfinder forum...

P0720 VSS A/T

[shahabc]

Thank you. I had previously replaced TPS and the problem did not go away. However, when TPS stay disconnected, I do not see this gear downshifting. I also took the car to Nissan Dealer and they could not replicate the conditions. The checked for any faults but could not find. Apparently, it is related to electrical system. Could it be due to malfuntion in wiring?Thanks