355 Slow down light issue

I have tried many things on what to do with the slow down light. To get to the bottom of it, it is easier and more direct to put the computer on the car. We have a ST5 here and would be willing to help out and diagnose the issue. Look at the airflow meter and see if it has any carbon or dirt on it. You could also try some fuel cleaner as this is something that seems to be an issue and brings the light on and puts it in slow down mode. We are more than willing to help you can call on 832-277-7062 and we can talk about the best things to do.

 

Filling out your profile might get you a better response from folks, for your generous offer of help.

 

Very interesting post for me...

My problem was the opposite...... my car did not show any red light nor check engine at the star..... and couldn't find what was the point.....

Will try to see if reconecting them the problem hapens and find how to solve it right....

regards and thank you.

 

Sooner or later access to replacement ECUs,... will start to fade or become impossible altogether. Thus, now is the time to start figuring out what voltages the ECU wants to see from the exhaust computers to avoid throwing a SDL and going into limp home mode.

I, personally, have already eaten a $600 exhaust computer (2.7) to make my issues vanish. I suspect a $0.05 resistor or two could have done the same amount of good in my engine bay......

 

Hello all F355 owners with this very often problem SDL light flashing or constant. My issue is similar with a lot of you - my car show suddenly flashing SDL and I ofcourse slow down even I am driving in normal traffic. Then after some minutes it get constant and after few seconds it turn off one bank. Yes the car does excactly what it should, to ensure no fire and accidents. But this information is a failure because both cats are with right temperture! I believe as everybody is written that the faillure comes from the ECU boxes and/or the thermo cables and the switch arround, tests with one at the time makes a lot of sence to save money. BUT after checking all this with new test parts my SDL are still there, after turn off battery one night and stone cold car the SDL are still there, constant and with only one bank running. We believe there is a information in the system which cant be deletet just only with disconnecting the battery. The system has an old information with values from ECU and we believe we have to find this in the system with a original Ferrari test unit and take out all errors which are disturbing eachother. If this dosent help we have an idea of some cables issues between the ECU's to the system which make the SDL and turnoff bank. I promise to send feedback on this when we find the finally reason. Thanks and greetings FerrariLund

 

Of course, wiring can be faulty. Also, there could be ECU issues.

Do you mean the SDL is there.. or the SDLs are there? Do you have a 2.7 or 5.2? I have wiring diagrams for both cars.

The manuals do seem to say that a battery disconnect should erase the fault messages (even on a 5.2 car), so it does sound like you have a hard wiring fault (because you are getting the SDL before the car is warm).

Do you mean you have changed the thermocouples?

 

The car is 5,2 motronic so only 1 SDL. And yes both thermo cables are new and also 2 new ECU boxes with green backside. Some guys write about TDC sensor but I think if that part has a problem it would not ask for the SDL. Thank you if you will send me the wiring diagram it will be next step I guess.

 

Thermocouples and Thermocouple ECUs are shown at the top (middle) of this diagram:

https://www.dropbox.com/t/1YxLn6CGvw5aVwZu

12 volt power comes in on connector 41090 (near the ECU)... green wire.. from relay "M" in the footwell

41090 is the same as 41051 in this diagram (which shows the relay).

https://www.dropbox.com/t/KTu1Oax1jmKjK1Jh

The relay is controlled by the ECU (with ignition ON)

 

Hello Qavion. Thank you for wirring diagrams. Are you saying if we i.e. find a broken wire by massage to the wires that the SDL will turn off while the ignition is on or do we have to start the car? or the only way is to check wire one by one?

 

I would do some basic wiring checks. It shouldn't take too long.

A high voltage output from the thermocouple ECUs = high temperatures. I'm not really sure what would cause that. Perhaps one of the signal wires (from the thermocouple ECU) going to the Motronics ECU is shorted to power.

Anyway...

1) I would first check the output wire from each thermocouple ECU to the Motronics ECU for continuity (with power off). i.e. purple wire on RH Thermocouple ECU to pin 15 and purple/white wire on LH thermocouple ECU to pin 14.

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2) Make sure your thermocouple ECU earths are good (black wires)

3) With ignition power on, make sure you are getting 12 volts to each Thermocouple ECU.

4) You can simulate a good thermocouple and thermocouple pair by putting a zener diode and resistor in the circuit like this:

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See a full explanation here:

https://www.ferrarichat.com/forum/posts/145063021/

Others have used a 1.5 volt battery instead to simulate a normal signal (i.e. not an overheat).

The next step would be monitoring the voltage on the purple and purple/white wires. There are some forum message threads on this. Hopefully you won't have to go that far.

 

Hello Qavion, thank you very much - I will save and remember this until later because today I can confirm one thing. Today we finally got the original Ferrari tester which only operate with Windows 7. In here the car has a lot of errors and values which need a reset to the original values with this software tool. After this my SDL went off and the car start in normal mode with all 8 cylinders. Therefore one thing to be clear and to a lot of threads "it is not enough just to release the battery for minutes, hours, days and then believe all errors are gone"! today I got the prove in this. One more big thanks to Qavion for your support For now I will try the car, hopently without any SDL troubles again and if the SDL comes again I am pretty sure there is a wirring issue somewhere and have your explanation and diagrams. I will post later about the situation. All the bests guys

 

Interesting, thanks. I think it's fair to say that not all 355s are the same. Others will swear that the battery reset will clear the Motronic ECU error messages. I assume you are in Europe? Perhaps Euro 5.2 ECUs are different?

 

Yes, you can have a point in this and also differences between 2,7 and 5,2 motronic. Mine is Europe 5,2 from 11/1996. For now I hope the SDL problem is solved with check/changes of cat-ECU and Thermo couples and with a reset of motronic with original Ferrari software tools. Anyway I will keep you all posted, but need to drive several month, thanks

 

After all the darn help and detailed posts you got regarding this you didn't give a DAMN to update the thread as to what the solution or outcome of your problem was..another dead beat forum non contributor.
(i know its an old post, but sucks when you go through and these guys never update w findings)

 

Any findings here? Would be helpful for many.

 

I also have a version of this issue- installed Tubi headers on 98 (5.2) Spyder. Right bank running much hotter than left bank in general (about 100 Deg F hotter at collection pipe prior to cat entry-idle rpm). Getting SDL at mid rpm range 4500 or so) at highway speeds and bank shuts off etc... Trying new thermalcouplers and Catalyst ECU x3. Interestingly, my left bank catalytic converter behind aft O2 probe is very hot compared to right side cat-about 300 degrees F hotter at idle. Car seems to be running smoothly, fixed a missing cylinder on left side #7 had a dead plug and upon inspection of stock header once removed, had immense carbon buildup in the manifold for that cylinder.

Certainly, seeing outcomes and fixes as follow-up is the intent. F-Chat has been very helpful to me as I try to recondition my F355 as my first Ferrari. I am a convert, as never drove one before and am sold now so thanks to you all for being a great community that assists us that wrench ourselves. My best and thanks.
GSL

 

Right bank hotter than left before cat, left bank cat hotter than right bank cat = you have unburnt fuel in left bank exhaust. Left bank is running rich.

 

Thanks-I suspected that the left if running rich, will be investigating that issue, certainly was for long time with #7 being out but that is fixed. Will test spark on that bank to see if we have a miss-from how she is running now, does not appear so. No CEL issues.
Appreciate input.
Gregg

 

Not just ignition, but other factors too. I am in no way a technician, but when I had my 355 spider serviced at the dealer, not only did they send photos of them degreeing the cams precisely, they also used a flow device to synchronize all 8 throttle bodies. They advised many shops (even dealers) would shortcut the process and skip these required services and end up with a poorly running car.

 

Last night I did some scans with OBDII reader trying to understand my issue: received following codes, 98 F355 Spider (5.2).

P0153 O2 sensor circuit slow response Bank 2 sensor 1
P0159 O2 sensor circuit slow response Bank 2 sensor 2
P0102 Mass or Volume air flow sensor A circuit low
P1454 Differential Pressure sensor flow too high
P0137 O2 sensor 1/2 circuit low

Since the car sat prior to my ownership without running, and in the process of getting it running again, I found #7 cylinder with a dead spark plug and large carbon deposits in the exhaust header when I changed the stock units to Tubi. Thinking bank 2 is running rich (based on previous evidence) I tested each fuel injector while car running by unplugging and looking for cadence change. Both #8 and #7 were not operating properly and the cylinders cool and not firing. Used a trick learned from Iain Tyrrell by stimulating the injector with leads attached to automotive battery instantaneously to get them unstuck. This worked on #8 and partially on #7. Much better response from both cylinders. Will run with some BG44 to see if it cleans that up. So, some progress on this issue.
GSL

 

Why not send the injectors out for cleaning and balancing? It is not terribly expensive. My dealer did that for my 97 355 spider when I hit around the 54,000 mile mark and having a major service performed. That way you will know for certain they are operating optimally.

Attached is a picture of my car getting the throttle bodies synchronized. Not a great photo, but the only one I have. This was at a tech session at my dealer for the local Ferrari club...they also swapped the wheels to show off a new factory Speedline wheel option being offered at the time. They thankfully but my stock ones back on... This must be 9 years ago.

 

Might want to start with the O2 sensors. With those codes the CEL should be lit.

 

@ddg599 Seems like you have some substantial problems. IMHO with a car throwing that many codes that sat for years, it's best to start off by 'baselining' the engine. Or else you're going to play whack-a-mole with problems. I would get the injectors cleaned and flow matched, make sure all your plugs are good or replace them, test the ignition wires, clean the MAF, smoke test the intake and exhaust, visually inspect the cats (the matrix tends to break loose), and test the o2 sensors for resistance if not replace them.

 

P1454 is cat protection active, bank 2, which agrees with you left hand cat being hot and bank shut down. Again, bank 2 running rich or misfire.

 

No CEL and I know it is working.