Thermocouples, slow down lights, related CEL’s, and how to conquer them...

You say, "didn't reset". What does that mean? SDL still on? Or just that the car is running poorly.

 

Good point John

 

I did the old assumtion thing again.

 

Has the car stood for a longer period of time with old gas?
The rubber gasket of the fuel pump in the tank might have dissolved, and is blocking the fuel supply.
That would give it intermittent problems like hiccups and low on power.

Because if the car is in safe mode because of the SDL/Cat/thermo, the SDL should be lit solid, and you would have a very bad sounding 4 cylinder. You would know.

 

Thank you for getting back to me, I shall take a good look at the fuel supply and have just taken delivery of a new fuel filter. I don't think its old gas/petrol as the car was running fine until this fault occurred whilst I was driving. I will get back to you and answer your questions as soon as I have time to take another look at the car, which probably wont be for the next 3 weeks or so.

 

I thought Phil had isolated the problem to one bank?

Would a faulty bank fuel regulator or an air leak produce these symptoms?

Without talking to the mechanic, it's difficult to know what data he looked at. Was he only looking at messages? Did he use an exhaust gas analyser, etc?

 

I have to admit that I wonder why a car driven hard, an SLD is triggered which leads to a bank shut down, car limped home, and then doesn't run right after cool down leads to a fuel delivery problem. I'd be wonder about the condition of the cat on the side that shut down.

 

If it 100% sure that it is running on one bank, than the problem is not likely fuel pump related.
But one bank shut down would mean a SDL lit solid.
Maybe I missed that info?
But a car down on power, and not running well, can sure suffer from a fuel pressure that is too low (or too high->fuel pressure regulator ).
I have had both symptoms on my car that had stood for a year before I bought it.
Pressure was restored with a new fuel pump(old one had completely clogged) and SDL problems were caused by cat connectors (front-back) switched on both sides. Or at least my sdl days were over once the cats were reconnected properly, blue ribbon etc.

 

Maybe it's time to review the SDL system.

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Maybe the N factor has come into play? With a lot more time needed to reset itself?

 

I also have been getting a intermittent SDL last year I had a belt service done and since then (not all the time) when the car is either at idle or when I'm doing city driving I get a couple of flashes from the SDL, However when I'm driving at higher RPM (highway) I don't get the SDL.

 

at the highway(speed) there is more cooling air around the exhaust and cats, which lowers the temperature.

 

Yup what he said

 

Good day to “The Brain Trust” of all things F355! I’m stumped. Like many of my 355 brethren, over the years I’ve owned my ‘96 GTS I’ve had bouts with erroneous slow down lights. Occasionally, the Motronic (5.2) would shut down a bank briefly but not very often...maybe once a year. I’ve used “jevs” method to test the SDECUs and thermocouples and also made a couple of his devices to “trick” the system, which worked great! But during that time, I was using test pipes (actually they were de-cored catalytic converters..GA inspectes for cats). A few years ago I was rebuilding my engine - a long story- and I decided to at least put high flow cats on the car. All systems were working properly for a few months, but one evening I was driving the car and the flashing SDL came on, and continues to flash as soon as the engine starts. It has not gone away

Here’s what I’ve done (before I gave up)

- verified that the cats were not over heating whether at startup or on the road
- revisited everything SDECU, SDL, etc on FerrariChat
- retested all of my SDECUs, thermocouples
- purchased two new thermocouples (just to be sure : ))
- checked continuity of the wiring that is related to SDL
- tested the SD system in situ

And here is my findings/dilemma. At start up, there is .5V leaving the SDECUs and that amount of voltage is entering the Motronic at pins 14 and 15. As the cats start heating, voltage is exponentially rising and that voltage is also reaching pins 14 and 15. Here’s where it goes off the rails. Pin 66 (SDL) is always emitting a fluctuating 4v-12v...hence a flashing light.

So, my question to all of you is; has anyone ever taken the Motronic ECU case apart and looked at the circuit board? I’m pretty damn sure there's a bad circuit and or “solder” or diode or something simple like that. But before I remove the case, I would like to know if there are any problems getting the case apart? Like sealant, glue, stuff like that...

My sincerest thanks for any/all, comments and suggestions

Randy

 

Did you test all 3 TCUs? do they all do the same thing?

 

Thanks for responding yelcab! Yes I did a test on all of the TCUs I own ( I’ve accumulated 7 now including the new TCUs I bought from Ricambi) I probably should have mentioned that I also inserted the “jevs” device that puts out a steady 1.5v and have the same outcome = 1.5v into pins 14/15 and oscillating voltage coming out of pin 66. Thanks again for the question/comment ! It never hurts to ensure all the bases have been covered

 

Other than Ferrari, do other cars have a separate cat ecu that turns off a bank of cylinders if it senses an overheated cat?

 

There is one more thing I suggest you do before you blame the ECU to be at fault.

Reset the error condition with a OBD2 scanner. Clear the CEL and then give it a 1.5V steady signal to see if you are still getting the SDL coming out.

 

Great idea! I’ll give it a try and report back soon. Thank you again for the suggestion

 

Maserati of course!

 

Same family doesn't count

 

Had a little time to try your suggestion this morning. Here’s my method and out come:

First, cleared the codes from OBD (1445, 1449)

Next, attached two separate 1.5 volt Alkaline batteries to the SDECU circuits and verified the battery voltage at Pin 14-15 at the Motronic ECU

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Started the car and still had oscillating voltage coming from Pin 66 and the SDL was also flashing.

Reconnected the SDECU circuits and checked voltage (ignition on) going into Pin 14-15

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SDL still flashing with this voltage too. Although I had completed these tests before, it was a worthwhile exercise for me...just to make sure I did them correctly the first time! Let me know if you have any doubts or concerns about the method I used. Thank you again for time, patience and suggestions : )

Randy

 

Randy did you check your thermocouple.

I think mine were original because in the last 15 years i have replaced two of the ecu's of the 3.
Just finished my 3rd service and the sdl came on . I only had this happen each time and replac d ecu. Very inconsistent.
This time the ecu was not the problem.
I changed the thermocouple reset with obd and so far so good.

I know with my setup which I have been running for a long long time hyperflows and cappi and groupe intake I fought for years with intermittent cel but after buying minicats in 2010 have not had a cel since unless there was a problem.
Only one i remember is a coil stopped working.

Sometimes the thermocouple acts intermitent.

 

While you have the batteries attched clear code with obd2 again
Key on engine off
If this does not work then do following

Then drive car with batteries hooked up and let cats warm up and after 20 min drive shut off car
Reset obd again
This is what i had to do.

It seemed like the box has a memory and it needs to see good results, then cleared before it goes away.
At least mine did
Good luck

 

This the voltage coming from Pin 66

Thanks for the response Taz! I’ll give this OBD Reset regimen a try. I can almost see the logic within the Motronic, since it’s software/firmware relearns the engine parameters after a disconnection with the battery. It’s certainly worth a try!

I have 3 new thermocouples on the car (less than 500 miles old) that I bought from Daniel @ Ricambi America. Like yours, my TCs were old...they’ve been on the car since I bought in 2007 and who knows how long they were on the car before I bought it. I still have the old TCs and they work okay based on the test method that “jevs” used at the beginning of this thread (heat gun and multimeter).

I do appreciate your input and I’ll document what my method and respond back to this thread. If you think of anything else, don’t hesitate to share