Recently during a two drive the speedo became erratic even though the RPM remained constant while on the highway. The engine check light was already on due to the up stream O2 sensor needed to be replaced. Next day zero reading on the speedo and hesitation with shift points. Sperdo occasionally showed a reading then fails back to zero.
My car has 180500 miles.
My car has an automatic transmission.
From your description it sounds like either the speed sensor is bad or there is a problem in the wiring of the speed sensor circuit. Your transmission is shifting weird because the car does not know how fast it is going. The tachometer uses another sensor to determine the speed of the engine. A YourMechanic certified technician can come to your location to help you diagnose and repair this issue by performing one or more of the following services:
Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing