355 goes into 'Limp' mode

O2 sensor computers should be 3 of them this happens with test pipes very sensitive try unplugging the o2 and thermocouple plugs and cleaning the plugs and resetting them , to find them just follow the leads to the cats.

 

First of all welcome to Ferrarichat.

What you describe is a very common problem usually associated with bad catalytic converter temperature ecu/s. The Cat temp ecu/s "think" it/they are getting an over heating signal from the thermocouple, send that signal to the Motronic engine management, and the engine ecu shuts down the bank of cylinders it was told is "over heating" the catalytic converter.

Run a search of the archives for more reading as this has been discussed many times, and you will have plenty to read.

Your biggest issue will be determining what cat ecu is giving the signal. The reason is, if my memory serve me correct, you only have one slow down light, where as the older 355's ('95) have two slow down lights, making it much easier to swap the cat temp ecu's from side to side to see if the light follows. If it happens again, that you car goes into limp mode, what you want to do is unplug just one of the cat ecu's and see if the limp mode goes away. The engine will run with the cat ecu's unplugged, but you will get an engine code for the unplugged cat ecu. If the engine is still in limp mode, leave the first one unplugged and then unplug the other cat ecu. If the limp mode goes away, you've found the problem cat ecu, or the bank that is "over heating".

Again run a search of the archive, as there is plenty of info on the matter.

 

Any change of getting the cats from the previous owner to temporarily swap in for the existing test pipes in order to pass emissions? Some do play this game. Also you best have a look under to know if your test pipes have a fixture for O2 sensor or temperature and if the sensors are still in the area. The drawing below is found in the 1997 US 355 Owner's Manual page C15 which you should have. Note cats are highlighted and the sensors ballooned as 'A' and 'F'.
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You can also try and reset the ecu's. Turn the car off at the isolator switch in the front luggage compartment. Leave it off over night.
Turn it on in the morning, turn everything off in the car eg air con radio etc. Start car without touching the accelerator, allow it to run without touching it for about 10 minutes Turn it off. Re start it and take it for a drive steady acceleration. The ecu will reset and re learn the fuel management systems and May, may fix your problem.

 

5 replies and nothing about the mileage???? 75k! wow! you've got one of the highest mileage 355s on this board! lets see some pics of this rare beast.

 

Yes, there are learned parameters that get erased when you turn the battery off. Akin to when you loose the preset stations on your radio when the battery gets disconnected. What you will need to do is let the ecu's relearn the warm up parameters. When you first start up the car, after the battery has been reconnected, you will want to just let it sit and warm up on it's own without touching anything for at least 10-15 minutes. I let the car sit and idle until the cooling fans kick on for the first time. Or, you can get a trickle charger and hook it up when you aren't using the car on a daily basis. Of course after it has relearned the parameters.

But,

This will not get rid of the limp mode.

You said that your CEL and SDL have been disabled. They probably took out the bulbs in the dash. That way you wouldn't see the CEL because of the secondary O2 sensor saying that the emission for the nonexistent cats (don't know if you still have the test pipes in?) being out of spec. Pretty easy to remedy that, just remove the dash pod (only 2 screws holding it in place) and put in new bulbs.

If you still have the test pipes fitted and you are getting the limp mode, I am pretty confident it's a bad cat ecu, or a bad thermocouple. Because there is no way you can over heat a test pipe.

 

did you allow it to re learn tis morning? on the 348 turning off the isolator switch will clear the cel warning. Not sure about the 355

 

It will not, on the F355.

 

According to my local Ferrari dealer, the right side catalyst ECU is the most common to fail. I believe mainly due to the location, it is much lower, and closer to the ground allowing for water intrusion from road spray.

If you are not aware, Ferrari updated the catalyst ECU's and the later versions have green epoxy potting, versus the early versions which were black. Make sure if you order replacements to get the later green ones (the black epoxy is known to seperate from the black plastic housing, allowing for moisture instrusion, the later greens is more resistant to this problem). Some try to find good used ones, but if you end up with black, you are bound to have more problems.

 

I have had the cat ecu's completely remove from my car for years. So yes the car will run with them disconnected, and I'm not giving you advise that I don't follow. Those damn cat ecu's are nothing but a pain in the ass. The only reason the cat ecu's are there are to "prevent" the cats from going bad, that's it. Even then they SUCK because 348/355 cats go bad all the time. I'm assuming you still have the test pipes? If you still have the test pipes then don't worry about it. Drive the car until it goes into limp mode, then start disconnecting them one by one until the limp mode goes away. Keep in mind this is a total caveman way of figuring out what cat ecu's is bad. Just remember you will get a engine code on your 355 with them disconnected.

I haven't ever pulled the codes from a 5.2 Motronic, but I'm assuming that being it's OBD2 you should be able to get the codes for exactly what cat temp ecu's is telling the Motronic it's getting hot????? Again I'm totally guessing on this. Can someone with a 5.2 verify if their auto parts store scanner can identify what cat temp ecu is giving the over heating signal? I have an Actron OBD2 scanner for my other cars, and it reads the sensors, and can give you live data, but I don't know if the DIY scanners can read the cat temp ecu's on our Ferrari. I'm thinking "no".

One more thing.

Did you ever get those CEL / SDL bulbs put back in?

 

Yes, if the CEL light is on, the OBD2 scanner will read the error codes for cat ECUs and tell you if temperature is out of range on bank 1, or bank 2, or bypass valve.

 

Thanks Mitchell. What brand code reader, and what model are you using Mitch? That way he can just go buy one and have a much easier time of finding the bad cat ecu.

 

I bought the one at Kragens (now Oreilly's). They have 3 models of one brand. I have since returned it because it does not work on live data mode as advertised on Ferrari.

 

You NEED to fix the CEL bulb, that one is important. As for the SDL you can leave that one out. But fix the CEL bulb.

 

+1. Consider the CEL to be your first line of defense in preventing engine damage. The light is advising you of a Pcode and you need that early warning to take care of whatever it is.

 

Since it is a federal standard, ANY OBDII code reader should work. Assuming he has had the recall work performed on the OBDII plug, which it sounds like he has, since he has scanned it once already and read the codes.

 

If you have the straight pipes, you will always have the CEL with 2 codes. If you unplug the ECUs, you will always have the CEL with 3 codes one for each ECU. So if you are going to drive it that way, the CEL is not going to do much for you in terms of warning because it is always on.

 

Hugh,

What is a Pcode?
Thank you

Tyler

 

P1448, P1228, P0223, P0425 are all error codes read by the OBD2 scanner. P0xxx are generic codes that all manufacturers have to support. P1xxx codes are proprietary manufacturer specific error code.

For example, P1448 is a Bypass valve error code that is specific to Ferrari, but nobody else.

P0401 (I think) is a generic code for Catalyst below efficiency, bank 1.