I have a 2007 Mazda 3 sedan with the 2.0L engine and 4 speed automatic transmission and about 127k miles. In the last year I have replaced the ECM/TCM (one unit), replaced the battery, and the Neutral Safety Switch. I am seeing a sporadic issue while driving down the highway, the gear indicator and gear speed display on the dashboard disappear and the car has a slight hiccup before resuming. I am not getting any warning lights on the dash and the DTC is not recording any issues. Any idea what I should look at next?

 

I see there are no comments but I did want to share what I am doing. Again no codes but I have been driving the car and noticed the following: I unplugged the transmission speed sensor control to clean and noticed after that the car faulted a lot less, I also noticed the engine speeds were periodically changing (at first I thought it was a downshift that was not displayed), and this sensor is $30. I have ordered a new sensor (OEM FN1121551) to see if this corrects the problem. The only thing I am not sure about if this is the only sensor or if there are more; this one is mounted on the transmission at the output shaft to the right wheel.