What is this?

[Jeo]

While driving home the other night I heard a noise that sounded like something repeatedly hitting the bottom of my car. I had just loaded up my boot with a pile of small metal rods, so I just figured it was one of them bouncing around and since I was only about a minute from home I just continued on. Got home, unloaded the boot and thought I'd better check under the car too, just to be safe. I saw this...





Its a pair of wires with a small yellow plug on the end. Its trailing out out of some part of the exhaust (the cat? wow I'm mechanically minded).

I found another similarly sized yellow plug that had nothing connected to it so I assumed thats where it was meant to be. Both plugs were fairly well smashed up, so I hard soldered them together. I could still see which wires were meant to connect to which from the shape of what was left of the plugs.

So back to my original question, what is it and whats it do?

[Juffa]

You have a Roadster, right? If so that would be the 2nd o2 sensor. Not sure what the implications of it not being connected are?

The local MX-5s have a o2 sensor before the cat, where at the imported versions have a sensor before and after. Might be to alert you that the Cat is faulty?

J

[jules]

wot eee sed


Jules

[Garry]

You may have an error logged on the ECU diagnostics but it wouldn't affect the way the car drives.

[Steampunk]

... where at the imported versions have a sensor before and after. Might be to alert you that the Cat is faulty?

J

One of them is a temperature sensor .... right?

[Jeo]

Cool, good to know. Thanks guys.

And yes, sorry I should have mentioned in the original post but I have an imported NA6.

[Russellb]

it is a Cat temp sensor
There is a light on the dash to say if the cat is overheating

Won't log an Error on the ECU as you have an SM4



Edit My Bad You have an SM4

[GP]

There is a light on the dash to say if the cat is overheating

Does anyone know what it means when the Cat overheats? Should I replace or ignore?

[bigdog]

Depends... if you're racing for pinks (in a ten minute drag race) then the passenger's side floor will drop off after the rivets explode.

[corners]

it is a Cat temp sensor
There is a light on the dash to say if the cat is overheating

Won't log an Error on the ECU as you dont have an SM4

As said its the Temp Sensor for the cat. I disconnected mine when the exhaust was changed sometime ago and have not seen the light nor had any problems with the way the car drives.

[muzza2]

yep agreed with above
i didnt have mine plugged in for about 2 years (due to it being snapped off when i got it.....)
got a 2nd hand cat which had one so i plugged it back in.
no difference to performance ect. ect.


P.S - love the Fast and Furious coments ;)