Cat conv warning light 95 740i

[Silver Fox 43]

I've got a 95 740i, does anyone know how to stop the cat light coming on please? I've had the cats removed, but the waning light still comes on. Thanks.

[martyyn 2]

Other than remove the sensors Im not sure you can.

Is it wise to remove the cats from one that has them ?

Ive heard you can seriously bugger your car if you remove the cats from an engine thats set up for them. It will forever struggle to get the right mixture wont it ?

Non techincal terms there obviously

[bumpstop325 0]

remove the bulb? if you can.

Put a black sticker over it.

[martyyn 2]

Right Ive had a poke around the old WWW as this was a subject very close to my heart two years ago when I had to spend 1k gbp for new cats.

Removing them is only any good if you have an engine remap....so I assume youve had that done. Otherwise the engine is going to be forever looking for a reading from the sensor that its not going to get.

You can remove the sensors, but they probably shouldve been removed when the cats were removed.

You _may_ get 15-20bhp by doing this but where you will lose is on the emission tests that are supposed to be coming in soon.

In the UK a de-catted 740 will fail its MOT simply on emissions....unless you spray some poxy stuff into it first and take it for a blat down the motorway and pray to the heavens.

For the short term in NZ you are ok, but Im sure they are supposed to be bringing emissions testing in, so you may have trouble, I dont know.

Personally I chose to replace them rather than remove them because at the time it was more trouble than it was worth to remove them.

So get down to whoever took them out for you (unless it was you) and get them to remove the sensors and disconnect the wires etc.

Otherwise as Tim says, take the bulb out

[cainchapman 0]

I believe that Remus (Retro products) do a high flow cat for around $600 each. Much cheaper than the $1500 per for genuine BMW ones.

I must say, I have had mine removed and have had no problems. But, as it was designed to comply with ADR regs, I don't know whether they did anything to the ECU.

Haven't dyno'd it since. Maybe it's time.

[Silver Fox 43]

Thanks Martyyn, I tried the old www, but didn't find much, suppose it's cause you can't do it in most places. I paid $90 to get them cut out and replaced with straight pipe, seems to run fine, and local mechanics all said it's done quite often. Only problem is the warning light still comes up when you start the car. Will have a play, and see what I can do.

[Silver Fox 43]

Any idea if the new regulations will be retro, or from new only?

[cainchapman 0]

In theory, if your car had cats fitted, they need to be fitted again.

However, no-one seems prepared to cough up the money to do the testing, so I can't see it happening soon.

[kiwi535 538]

are the oxygen sensors actually in the cat or much closer to the engine....they will still be sending a signal so the mixture will still be as lean as if the cats were there?

[Silver Fox 43]

I think they have one on either side of each cat.

[my_e36 43]

I heard there's O2 simulators available that lies to the ECU on its "reading". Not sure if this is the same as CAT sensors that you are talking about.

[Silver Fox 43]

Warning light says the cat's overheating, so I guess the cat sensor is in the cat, and different from the O2 sensors.

[gmccormack 0]

The O2 sensors are aways mounted in front of the cat, after all there is no point sniffing the exhaust gas to see if the engine is running in tune after the cat has messed with the true composition of the exhaust gas. The sensor in the cat is just for overheating. I think the light can be turned off by earthing the wire that used to connects to the old O2 sensor.