Toyota, Pre and Post Cat Sensors

[martins]

Car failed its MOT on emissions. Prior to MOT the EML kept coming on. I would reset. The error was one relating to emissions. On inspection the CAT was totally goosed. Have now replaced the CAT with a lovely shiney new one from 2ubular and have passed the MOT.....but....the EML is back on; first time with the same error code and then second time stating that there was no signal from the pre CAT sensor.........All of the above seems to indicate the pre CAT sensor is either goosed, has an intermittent fault or I have not connected it up properly after fitting the CAT. I suspect it is goosed.

I know that I can continue to run the car with the EML on but if the pre CAT sensor is goosed I will after a short period of time destroy the CAT as there will be no control over the emissions (£420 PROBLEM)

At this time I really do not want to have the expense of buYing a new sensor as they are not cheap. As I see it I have a few options but I also have some questions and would like advice on the following;

1. Swap the pre and the post CAT sensors??? Can this be done??? Are they the same??? Will this even protect the CAT??? What is the downside???

2. Remove the CAT and replace with a straight through silencer pipe which I have in the garage. This will leave the EML on but I also have a resistor which will allow me to bypass the pre CAT sensor so keep the EML off. Replace the through pipe with the CAT next Nov when the car is again due its MOT.

3. Stop being a pikey and buy the pre CAT sensor (this is least favourable as still suffering slightly from wife finding out about my spending on the car earlier in the year).

4. Ask Santa for a pre CAT sensor.

Any and all advice greatfully accepted.

Martin

[Mikie711]

If you have fitted one of Jim's 100 or 200 cell cats then what you need to do is fit an O2 sensor extension to the post cat sensor. This takes the sensor out of the exhaust stream and stops it triggering a EML light. I had the same problem when I did the SC260 Elise.

one of these

You also need to check that the sensors are connected to the correct socket in the wiring loom. Had a similar problem with the Evora after the exhaust swap and turned out one of the sensors was plugged into the wrong socket. IIRC there are only 2 on the Exige and they are next to one another, but the wiring is different colours for pre and post cat.On MY08 and later cars the pre cat wiring is Green/blue, Blue/yellow, Blue/red and Green/slate. The post cat is Purple/blue, Green/yellow, Green/slate, and Blue/red. Look at the wiring into the plugs on the car side of the loom and peal back the cover tape. Then look for the plug that has a Green/yellow wire and that is your post cat sensor. Make sure that is the sensor that is connected to that plug.

[Gourlay83]

To add to the above.

The Primary 02 is used by the ECU to trim the fuel mixture on CLOSED loop (idle or steady throttle), the secondary 02 basically measures the efficiency of the CAT. Spacing the sensor away from the exhaust gases is an easy fix, and reversible.

Sports cats and secondary 02's don't work that well together. I had a similar problem and found that the cats do work, but take a lot longer to get up to operating temperature (probably to do with surface area).

Fit a spacer, and forget about it

[martins]

M and A.

Many thanks.

Spacer bought.

Rgds

M

[martins]

M and A.

Final comment.

Spacer now fitted. No EML.

I am not at all sure what the reason was for the last CAT getting 'lunched' but with everything now up and running with the 2ubular sport cat and sport repackable back box the car is a completely different beast. I have had the sport box fitted since last winter but the previous cat was 2nd hand off Mike's 260 111r so no idea what conditions that was in when it went onto the car. With that fitted the car was one noisey beast and used to run really rich popping and banging all over the place. Now it does not have such an aural soundtrack but the performance def seems to be improved. Might it be that the engine was always running too rich thus impeding the performance?

One last question.

I have a further cat pipe in my garage which appears to have no contents in the cat part of the pipe. Just an MT bulge in the pipe (oh er missus). If I fitted this would it increase the performance of the car, or would it just sound like the car performance has increased? I know it would fail the MOT emissions test but then I could always fit the cat prior to the MOT.

martin

[Gourlay83]

One last question.

I have a further cat pipe in my garage which appears to have no contents in the cat part of the pipe. Just an MT bulge in the pipe (oh er missus). If I fitted this would it increase the performance of the car, or would it just sound like the car performance has increased? I know it would fail the MOT emissions test but then I could always fit the cat prior to the MOT.

martin

Technically anything you do to increase flow in and out of the engine will increase performance (to a point), but as you've already got a sports CAT the gains (if any) would be minimal.

The only advantage would be saving the life of the CAT, I think i've destroyed every Sports CAT I fitted (mainly due to track use). Using a De CAT for track etc wouldn't be a bad idea.

My opinions only of course.
Alan

[robin]

I seem to remember reading that you need to store cats properly when not in use, so if you do take this route, maybe wrap it in a cloth and keep in the airing cupboard. So long as the better half doesn't spot it!

Cheers,
Robin

[martins]

I think I will retain the cat for road use and use one of the 'old' cat pipes for track days. Getting quite good at swapping out the cat pipe and suspect I could also do it without taking the back box fully off the car.

Thanks again for the advise.

M

[alicrozier]

I've had one of Jim's Cats on the Exige and transferred it to the 211. Pretty extreme use on many, many trackdays and no problems.

Personally I wouldn't worry swapping them for trackdays...unless the worry is noise.