How to replace rear O2 sensor. Mk2.5 S-VT

Technical Area Engine, Transmission, Exhaust etc
2

My car has thrown up a P0037 code. If I knew how to take a screen capture I would have, but for now, this pic will have to do.

I intend to replace the rear O2 sensor, but, have a few questions.

1: How do I access the sensor - from the engine bay or from underneath the car?

2: What size and shape of socket will I need to use? I have a 22mm long socket, but, depending where the sensor is, I’m not sure it would be the best.

Thanks in advance.

 

 

3

Hi

You will need to access the sensor underneath the car, preferably in a pit or with car on a ramp. Post cat sensor is about a foot behind the catalytic converter, fitted to the central box section.

You will need a 21mm, six sided socket - don’t use the 22mm, it will likely round the lambda nut off. There are special lambda sockets that allow the sensor to be removed without cutting the wires but this only required if the lambda is being reused.

I think yours should be quite easy to get access to once you are under the car. Be aware that these can take considerable leverage to undo.     

 

4

Thanks for the quick reply. It’s a 22mm lambda socket I have but I don’t see any 21mm ones for sale (yet).
As for the new sensor, I see MX5 parts sell IL motorsport ones for considerably less than the Mazda one. Can I assume this is ok for every day road cars too?