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

+1000, and not to take anything away from what Jevs has done, but for anyone who still has cats on the car, this bypass solution is literally playing with fire. When I first started researching this system I couldn't believe that a Ferrari had this when so few other OEM's did, even those OEM's who use the same main ECU's. Surely Ferrari could have saved a few hundred $$$ by not putting it on, but then we discovered they had a very good reason for including it.

Apparently if you have ignition misfires, the main Motronic ECU's don't always catch them. In fact, you can have one bank of the engine not sparking, and the Motronic on that side will continue pumping fuel into the cylinders, and out the exhaust. If the cat on that side is still hot enough, the fuel will ignite and burn in the cat, and could and has caused a fire. http://www.ferrarichat.com/forum/showthread.php?t=388515&highlight=fire


So if you no longer have cats on your car, then Jevs' system is what you need, but if you still have cats, you really need to think twice about bypassing/eliminating this system. This is why I opted to work with Aerospace Logic and develop a more reliable cat monitoring system. I know this sounds like a sales pitch, but it's really not - it's a cautionary advise.

 

Just right here!!, FARRARICHAT, this is my favorite place!!

 

Just want to thank Jevs for the research and tests he developed, AND shared with us, as I have been plagued with slow down lights for several months now. I have an MS Racing exhaust, with hi flow cats, and I have been getting the P1445 code... And through duplication of Jevs tests I determined that my passenger side Cat ECU is defective ( I.e, not giving out any voltage at the signal terminal), got it replaced, and no slow down light! The other ECUs are fine, so I just reinforced them with new solder joints at the terminals so hopefully they will give me many many more years of service.

I drove over 100 miles since the repairs with no SDLs, I am happy!

Thanks again!

Now to tackle the P0410 code that I still get every so often.

 

Hey Jevs,
Do you know what pin on the 5.2 Motronic is connected to the trigger/signal wire from the Bypass ECU?
I have an Australian 5.2 355 with a USA ECU so its looking for this signal but the harness does not have these wires. I'm hoping to use your solution to feed it the signal it wants.

Thanks for taking the time to post great info like this for the rest of us.

 

pin 56, for a full list, search 355 ECU pin out and wiring colors

 

That's an impressive piece of work you've done there! It will save me a HEAP of time.

On you list it says pin 56 is for Ignition Lock but I'm hoping to find the pin for the trigger/signal from the thermocouple ecu that monitors the temperature behind the bypass valve in the exhaust. From reading your list I'm guessing it might be pin '73 Purple Temperature AGK' but I have no idea what AGK is.

Thanks for your help.

 

That is the UNKNOWN pin on the list. I since figured out what that pin is for.

 

Just to clarify, do you mean that 56 is not an ignition lock but is in fact the signal wire from the bypass pipe thermocouple ecu?

Sorry I might have misinterpreted what you said.

Thanks again.

 

What the 355 braintrust needs to do is perfect the work drbob1 started. He has just 1 bug left and his system leaves cat overtemp system intact. It is not a bypass like mine or Jevs and his solution is cheap.

 

No,

Pin 56, Ignition Lock, signal from the Immobilizer that tells the ECU to do its thing.
Pin 42, Pink Black, analog signal from the By-Pass valve TCU that turns on the slow down light if it is too hot.

Previously pin 42 was function unknown.

 

The EGT solution which Dr Bob was following up on works but the problem was that when cold it would output less that 0.5 V which would cause the SDL to come on until the exhaust warmed up the TCs. He was working with EGT to modify the black box but there was a cost issue in that the electronics would have to reengineered. I believe there is a fairly simple DIY solution to the problem but I haven't gotten around to looking into it yet. I can not say wen of if I will.

 

Ah-ha. I just tried feeding the 0.5V signal to pin 42 and unfortunately it's not working for me for some reason. What I find odd is when I feed it 0.5V it lifts to 0.8V for some reason even though I disconnected the original wire from the pin. I've dropped the input voltage to 0.25 which then lifts to 0.5V but the SDL is still flashing away. I followed all of Jevs tests and both cat ECU's are working fine from what I can see. I'm worried the spike in voltage is a short in the Motronic.

Any thoughts?

 

Yes 1.5V shuts the light off. If you are chicken you can prove it with a 1.5V drycell battery like in your wireless mouse.

 

Yes I read your awesome thread on this but doesn't the Motronic look for 0.5V from the bypass valve SDECU rather than the 1.5V needed to delete the two cat SDECU's?

After reading Jevs thread, I believe this is because the bypass valve SDECU tells the Motronic if the bypass valve is open when it shouldn't be i.e. at idle and cruise. From what I've read on here, 0.5V is from 0F - 500F and if the valve is shut then it would be in this range so 0.5V should keep the Motronic happy in theory, especially at cold start but my light is still flashing, even when cold.

 

great tutorial!

 

My SDL was fluttering just before I dropped it off at the dealer for an F1 calibration. After picking it up the flickering was getting worse and I reflowed the ECUs without any improvement. I soldered up the simulators and installed them in the car opting for the aluminium cases flooded with silicone to keep things nice and sealed. After initially I went from a flickering SDL to a blinking one but after a 15 min drive the SDL stopped blinking and went dark.


A few observations.

1. I did the sanity check on the ECU harness resistance value and got 280 KOhms instead of the 312 K Ohms suggested, if one was off I would be suspicious but with all three I submit there was some minor change to the module.

2. When I was calibrating the module I did it live on the car to get the output voltage as correct as possible.

3. I do have a CEL without any codes I suspect was initiated by the SDL, How much mileage/drive cycles does it take to clear this?

 

Can't speak to a 355, but both SDLs were coming on randomly in my 348. Replaced one thermocouple with one supplied by DrBob and that side SDL has not come back on since, while the other side still comes on randomly. Still need to replace the second thermocouple to confirm, but I'm pretty sure they were the cause of my specific problem, which is surprising since they look great and the car only has 22k miles on it. FWIW, the TCs I got from Bob look to be better assembled than the originals and his prices are great.

Good luck and let us know what you find.

 

Also, does anyone know of a source for caps to install in place of the thermocouples?

 

The thread is m10x1. You should be able to search and find caps that size.

 

NAPA.

 

Hi, Jevs,

I noticed that in my F355, there is a wire on the 4th terminal of the harness connector from the SC ECU; and wonder what provisions we need to make for that, as apparently it's used for something. I've almost finished my build of the thermocouple simulator, and am concerned that we missed something.
I'm dealing with Casper on getting a part number on the specific 4 pin connector, will furnish it if you want.
Thanks, Al

 

I speak for a lot of folks on the forum, sorry to see you go.

AFAIK, that fourth wire ("Pin D") is only on the OBD-1 cars. Please see attached photo of the SD ECU harness connector on my car.

For the record, here is some data from the Ferrari schematics, which agrees with the insulation colors in my harness wiring:
Pin A = 12 vdc input (green wire)
[Next, connector guide pin/spacer here]
Pin B = ground (black)
Pin C = most probably the amplified thermocouple SD ECU output signal; violet/white wire. It leads to Pin 44 of the Motronic 2.7 ECU.
Pin D = undefined function. (red/black wire leads to pin 11 of the 2.7 ECU). This one concerns me a bit since it's function is unknown. FWIW: On another make of car that uses the 2.7 ECU, this pin is a knock sensor input. It might be a backup/ failsafe /bank-shutdown/ throw-a-code signal in case of a cat gross overtemp.
Thanks again for your hard work and input to the forum on this project.
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Jevs, just wanted to say this was one of the most logically, descriptive and to the point posts I've read here.
I was leary of my temp sensors, proved them out all good and onto other tasks now.
Great work!

 

Jevs this was some piece of work you created here, lots of intelligent info that i'm going to have a go at.
The problem i'm having is the light is flashing from cold and never goes off and never goes to solid Red,
Now i have decided to sell my F355 Berlinetta so i need it sorted, i'm going to start with checking all my connections first. Wonder where the bypass ECU is located must have a close inspection tomorrow.
Thanks Again