On my car, the RH cat ECU and the exhaust bypass ECU are close to each other. It’s possible to mix up the cables for the two ECUs if you remove them more than one at a time. Even my Ferrari tech has made this mistake. I don’t fully understand the fault logic in the Motronic ECU (5.2), but I think a comparison is made between the main cat temps and it realises that one cat isn’t heating up normally (as sensed by the incorrect wiring), even below the rpm that will trigger the bypass valve… and the Motronic ECU will generate a CEL.
Note that I didn’t mean mixing the plugs on the same TCU … that would be impossible. One is 4 pin, one is two pin.
I am not very familiar with the Technistrada products but, if I am not wrong, they make Cat ECU dummies which do not use any Thermocouples. Did you buy Technistrada Cat ECU dummies or Technistrada's version of working Cat ECUs and Technistrada Thermocouples?
Sorry, I misread that. Yes, if you are using the Technistrada bypass plugs, they plug into the harness going to the Motronic ECU. If you plugged one of the Technistrada bypass plugs into the exhaust bypass thermocouple ECU, that would cause issues. The RH cat thermocouple ECU should have green, black and purple wires (no stripes). The exhaust bypass thermocouple ECU has a purple/black wire.
I have all of the above. I started to change the Cat ECU, then I changed the thermocouples. When that didn't help I disconnected the Cat ECU and added the dummy load. No difference, the SDL still flashes as soon as the engine starts.
I have checked again and I cannot see any connectors in that area that are the same as the one that was connected to the original Cat ECU. I have attached two pictures of the connector on the RH side. Image Unavailable, Please Login Image Unavailable, Please Login
Interesting. Perhaps only the US/Canada/Australia cars have a 3rd cat thermocouple ECU: Image Unavailable, Please Login Do you actually have a thermocouple on the bypass valve (as shown in the image above)? If so, does it go directly to the Motronic ECU? I did hear that some cars have different wire colours, but I thought that was on the O2 sensors.
Btw, I noticed that there is a empty hose connector and a cut off hose below the pump. Is this normal? Image Unavailable, Please Login
There should be a vaccum source on the bottom hose and the top hose should go to the bypass valve. Image Unavailable, Please Login What is that T-section attached to? Image Unavailable, Please Login
It looks like your pipe setup will keep the exhaust bypass valve permanently open (whenever the engine is producing vacuum). As there is no feedback from a third thermocouple, I guess there should be no fault lights. I wonder if your vacuum solenoid is serviceable? Were the pipes rearranged to keep the valve permanently open or was it because the solenoid was faulty (and they decided to force the bypass valve to stay open)?
Is your bypass valve now operating the way it should? Do you still have the Technistrada bypass plugs fitted? That is, no thermocouple ECU’s?
I do not know, I have the car upon my lift and I'm alone so I cannot see if it opens or closes. To my ear, nothing happens when I rev it up. And since it's inside my garage, it still sounds loud on idle. Yes.
Because the car is new to you, I don’t know what the car should have fitted. I’m not sure if the previous owner fitted that thermocouple blanking plug to your bypass exhaust. Maybe you could check the Bosch part number of the Motronic ECU and we could see if it’s a USA type ECU. The ECU is behind the right hand seat. I assume you don’t have an OBD port on your Euro car? Do you have an OBD reader anyway? It’s possible to purchase a 3-pin Fiat OBD adaptor and a cigarette lighter power adaptor and wire up a connection to your Motronic ECU and get some fault codes.
If they removed the thermocouple from the bypass, I would assume that I still would have the box that it where connected to, the one you have. But I do not have that so I'm guessing that it might never have been there. I cannot know for sure though. The car was sold new in Italy so it has to be a Euro spec car. Again, I'm assuming, but this car never left Europe according to the registers. I do have a OBDII reader but I cannot find any port under the dash next to the steering column. Do you know where to buy the adapter? Anyway, I'm going to call my contact at the official Ferrari dealer here in Sweden tomorrow and see if he can shed any light on this matter. I have also sent an email to Technistrada to see if he can give me any tips on how to move on. Thanks for you efforts to help me get this resolved. It's very much appreciated!
I recall that on some 355’s that the bypass thermocouple is wired directly into the Motronic ECU. I think I saw a picture of this in the WSM.
Finally got some time to try and fix this again. No luck however... Regarding the bypass valve: I bought two new (used) vacuum solenoids on ebay thinking that it might be the solenoid that was faulty. I switched it out and it made no difference to the bypass valve or the SDL. I also tested the function of the solenoid and it closes and opens when I add 12V to the pins. So, I can confirm that the bypass valve only opens if I reroute the vacuum hoses (as it was when I got the car) When it is routed through the solenoid, it doesn't open. So my current theory is that the solenoid doesn't get the correct signal from the ECU. Regarding the SDL: Nothing I have done so far has made it go away so I have no clue how to move on. As I wrote previously, I have changed everything with the stuff I bought from Technistrada and it it still flashes. I'm wondering if the SDL and the problem with the bypass valve even have anything to do with each other?
I bought this: https://www.amazon.se/dp/B08NPWNTQW/ref=pe_24982401_503747021_TE_SCE_dp_1 However, the 3-pin plug doesn't fit into the connector behind the passenger seat. The pins in the adapter are too wide. Are there more than one variant of the Fiat OBD2 Adapter?
Bah... I just read the reviews on this adapter on ebay and it seems as more than me have had the problem with the pins being too wide...
I think this is where I ordered mine, supposedly from Australia. https://www.ebay.com.au/itm/355879819547? My car is in the workshop, though. I can't test it and send it to you. I think we need to start from the beginnning... (EDIT) The valve should be closed with the engine off and with the engine idling. The solenoid valves on your car look standard, as does the actuator, but they should not operate this way. There should not be vacuum at the valve to open it when the car is idling. I still think your pipes are not routed properly.... or you have non-OEM parts fitted. I just re-read what you said. You said that you have no thermocouple on your bypass valve, so there must only be one thermocouple on the right hand side of the car. Therefore it's not possible to mix up the plugs. Since you have no thermocouple on the bypass valve, I'm not sure if it's possible for the bypass valve to generate a CEL or SDL, unless (maybe?) a CEL is triggered if the resistance of the bypass solenoid valve coil is bad. It may be possible to mix up solenoid valve connectors. Have you tried doing wiring checks between the secondary air relay and the solenoid valve? Or wiring checks between the ECU and the bypass valve solenoid valve? Since you've changed thermocouples and thermocouple ECU's, you either have a wiring issue or a real cat temperature issue.
