P0031 Mazda -

Question

Checked voltage at connection for air/ratio sensor 2.5 volts indicated Fuse to circuit OK, 10 amp. any other checks that I can preform? Should voltage be 12 volts or???

Checked the rear oxygen sensor also it indicted 12.5 volts. No problem with that one.

Answer 1

P0031 Heated oxygen sensor , sensor 1 , bank 1

The voltage should be B+ ( battery voltage ) so this is correct, The next check is at the PCM, If there is B+ Then the problem is the PCM.