Disconnecting CAT ECU - any problems doing that?

I have had both my exhaust ECUs disconnected (and taped up) for awhile now. No problems. Obviously don't disconnect them if you have stock catalytic converters.
BT

 

With straight pipes, I can't see any reason to leave the cat ECU's in place.

Toss 'em in the rubbish bin!

 

I taped them off with black electrical tape. Not the best solution but the car is parked in the garage most of the time. I also zip tied the wiring looms to the rear subframe. It would probably be best to remove them from the car altogether but them you would have to cover the other end where they go to the engine management ECU I think.
BT

 

As said, disconnect them, there is absolutely no need for them. (they just monitor cat temperature, no other function for Motronic)

 

Mine has all the bits still in place and working, though essentially they are doing nothing (no cats). The guy probably left them in place in case you, or a future owner wanted to put cats in again. He did the right thing IMO.

 

please excuse my confusion...your guys are talking about the o2 ecu's "after" the cats right?

 

o2 sensors and thermocouples are two different thing, you don' want to remove o2 sensors but you do want to remove thermocouples. So this is just about thermocouple sensors and cat-"ECUs"

 

Since you are running test pipes, and you swapped the ecu's from one side to the other, and still got the light on the same side, I will say that you have a bad thermocouple.

However the good thing is that you are running test pipes, so you can ditch the ecu's all together. The Motronic ecu's will store a silent code (4121) indicating that it does not have a signal from the cat ecu, but you will not get a check engine light.

Disconnect away, and slow down lights go away.

 

Hi all; I'm a mechanic who specialises in trackday setup and engine/trans rebuilds, and I look after a 355 Challenge and a '96 355 GTS here in New Zealand. The Challenge car is Motronic 2.7, and we had a problem with the LH "check engine" light coming on intermittently and cutting the bank out. We did the usual things like swapping the air-fow meters, etc. from side to side, with no luck. Then I noticed that the air intake pipe to the LH bank had partially collapsed and had reduced the intake size by about 30%. I rectified this, and the problem went away and hasn't returned. My feeling is that the ECU was seeing too low an airflow measurement given the revs and throttle position, and elected to cut the bank out, just in case.

The 355 GTS, on the other hand, has a "slow down" light (Motronic 5.2, so only one light) that is flashing on all the time. This car has 3 thermocouple ecu's, and they're all cracked!!! Replacements are about US$650 each from the Ferrari dealer (only one in NZ, and it's 400 miles away...) I understand that these ecu's can cut a bank out if they set the slow down light to be on continuously, rather than flashing, so they must have a connection to the main ecu; however, I note that a number of members have just plain disconnected the thermocouple ecus and have had no problems. With three knackered ecu's this approach is pretty attractive, to say the least. Has anyone had a problem with this approach?

 

Does the car still have the CATS in place? If so there is the risk that they could overheat (a stuck injector causing rich running for example) and catch fire - the reason for the thermocouples in the first place. If you are able to run bypass pipes then you don't have to worry (though I am guessing in NZ this is a no-no for the road).

 

I would start a thread with this question specifically directed to 355 owners.
BT

 

I want to know too as My car is a 5.2 and I am redesigning my exhaust to a 360 style system and will no longer be using the bypass valve setup similar to the attached pic. So the pertinent thermocouple will no longer be needed. Any words

+1
Image Unavailable, Please Login

 

Sorry, I forgot to mention that the cats have been removed.

An auto-electrician friend of mine is looking into the issue, with a view to perhaps designing some sort of bypass plug that would convince the main ecu that the thermocouples are still there and working. Details when it happens!!

that's a good looking exhaust system. Any details on availability and price?