I have 2007 mazda 3 that gets po139 code. Should replacing the rear o2 sensor be the solution?

Question

No visible deterioration on the wiring harness. Any suggestion

Answer 1

Hi there,

Usually, replacing this sensor will take care of the problem. However, there are some other possibilities to cause this code such as faulty fuel injectors. Here is some more info for you. 

P0139 MAZDA - HO2S RR Circuit Problem

Read more: https://www.autocodes.com/p0139_mazda.html