CEL code P0031 - bad o2 sensor

YellowMP5

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2002 Mazda Protege5 YELLOW
The other day got a cel, code 31, comes back as front oxygen sensor heater voltage low. The car also runs bad and after a stop at a traffic light, hesitates (5-10 seconds) before actually accelerating forward.

I do not have headers on the car but do have autometer air/fuel gauge which was connected for the front oxygen sensor just after the connector.

So is my oxygen sensor bad? or is the heater part that is bad? where is the heater for the oxygen sensor, is it inside the connector itself?

I was looking through mazda shop manual (the .pdf that i dowloaded from mazdamotorsports website back in the day) and they explain how to check voltage inside the connector. But its confusing since apparently the peaple that put it together got the drawing incorrect. They have the o2 sensor (component side) connector listed as the harness side connector and vise versa. Those of you that have the manual can you verify? This is for the front sensor. They captioned the rear sensor drawings properly.

Anyways,
This is the only code that pops up. Those of you that had this code, was it the sensor? or have you had other problems too? have you replaced the sensor (about $300 from mazda) or have you done the cel eliminator?

help appreciated, thanks guys.
 
P0031 - resolved?

What was the resolution to your P0031 error? Did you have to replace the sensor, or what? I have the same problem with my '02 Protege...

Thanks!
 
Well now, me too. I have a 2002 Miata, with a code P0032, heater voltage high. Can I test the sensor I have? I need the correct electrical readings for the 4 pins.
 
wow, brought back from the dead.....

either the sensor is shot, the wiring is damaged/corroded, or the ECU is fried. most likely you just need to replace the sensor, protege O2 sensors are known to die out early, 20-30k miles.

if you have the shop manual you can check the resistance of the heater circuit on the O2 sensor, if it's not within the specified range it needs to be replaced.

BTW Protege Garage sells OEM mazda sensors for about $120. you will have to look or call to see if they have the sensor for your vehicle
 
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