Hello! I just installed headers and cat deletes and stupid me, I forgot which thermocouple plugs into which spot. The car runs fine with no CELS, I just want to make sure I plugged them back in correctly. In the attached photo, I have the bypass valve plugged into the upper spot and the right bank O2 into the lower. Can anyone verify if that’s correct or if I have them backwards? I couldn’t find anything online. Thanks! Image Unavailable, Please Login
Have you run the car since fitting the plugs? They will definitely throw a CEL if you have mixed them up. The Workshop Manual omits the bypass thermocouple ECU and just shows the RH Cat thermocouple ECU as vertically oriented Image Unavailable, Please Login The wire colours are hard to see, but bypass valve 4 pin plug should have a purple wire with a black stripe. The RH Cat should have a plain purple wire. If you can't see the colours, the only way to confirm where the plugs go is to carry out wiring checks between the thermocouple ECUs and the Motronic ECU: Image Unavailable, Please Login Pin 73 on the Motronic ECU plug matches the purple/black wire on the bypass thermocouple ECU Pin 15 on the Motronic ECU plug matches the purple wire on the RH Cat thermocouple ECU.
Thanks Qavion, I don’t think the wire colors will help me since I’m only trying to verify if the thermocouples are plugged into the TC ECU correctly. I suppose I should have been more clear. In the following pic, I have the bypass valve thermocouple plugged into the red circled plug and the right bank thermocouple into the green spot. There isn’t a separate bypass valve TC ECU and RH cat TC ECU. It’s one single unit. The car runs great, no CELs. Probably put 200miles on it so far. Image Unavailable, Please Login
Then why does your photo show two TC ECUs? One is vertical, the other horizontal. Image Unavailable, Please Login
Lol! You’re right! I just ran out to the garage to take a peek. I suppose I should have looked more closely behind all the vacuum lines lol It looks like I have them plugged in backwards. Strange, no CEL though. Thanks for your help as always! I appreciate it.
The main cat TC's are irrelevant with the cats deleted. Remove them, cap the bungs, install Technistrada dummy load plugins.
So, I swapped the TC plugs around and took the car for a spin and after around 5min of normal driving the Slow Down light comes on now. Strange. Basically, with the bypass TC plugged into the top ECU, the horizontal one (the wrong one according to the manual), the Slow Down light never came on after over 200 miles.
Image Unavailable, Please Login Image Unavailable, Please Login I just checked the wire colors on the 4 pin connector going to each ECU. The upper horizontal ECU has brown, black and green wires. The lower vertical ECU has light green, black, dark green wires.
It doesn't reall matter which TC ECU is used for which position .. as long as you plug in the matching (thermocouple and Motronic ECU) plugs. Unfortunately, I don't know which position is normal for the TC ECUs. My car's TC ECU plugs may have been swapped several times in the past also. However, since the bypass TC ECU is "additional" (and is not found on some F355's), you would assume it would be in the position not shown in this image: Image Unavailable, Please Login For the sake of logic, perhaps you should swap over the two pin thermocouple plugs to get rid of the CEL? Is this the config which generates the CEL? Which plugs did you swap over? The 4 pin plugs or the 2 pin plugs?
That makes sense. I've only ever unplugged the 2 pin TC plugs when I swapped the headers and cat deletes. The way I had them plugged in originally after the install produced no CEL (backward according to the manual). After speaking to you and seeing the diagram from the manual, I swapped the 2 pin plugs around. This produced the Slow Down light after 5min.
Have you followed the braided TC ECU cables to confirm what they are attached to? (EDIT) I just noticed that you said the wire colours are very different from the OEM diagrams. These are just some of many variations on different cars which are not reflected in the OEM wiring diagrams. The only way to confirm the identity of a 4 pin plug is to trace it back to the Motronic ECU pins. i.e. the bypass TC ECU plug is attached to pin 73 of the Motronic ECU. If you do decide to assign the horizontal TC ECU to a particular thermocouple, for future reference, you perhaps should label them to avoid further confusion.
Yes, I can physically see where the TC braided lines go on both ends(sensor side and plug side). The orientation that doesn't produce the Slow Down light is when the bypass TC is plugged into the upper horizontal ECU and the right side cat TC is plugged into the lower vertical ECU. I can physically trace the wires if you want me to verify them for you if you want to add that to your database. Otherwise, I'm tempted to just leave it lol.
You have basically done the wiring check for me by confirming which thermocouple is plugged into which TC ECU (and you get no CEL). If you restore your cables to the no CEL condition, this will match my "assumption" that the horizontal TC ECU is the "additional" TCU for the bypass system. At least one of the wires on the plug on the upper TC ECU will be connected to pin 73. Also, I have very little space on my 5.2 wiring diagram for adding notes about wiring variations However, if you wanted a personalised wiring diagram for your car, then you would have to tell me which colour wire on each 4 pin plug has 12 volts on it when the ignition is turned on. This way, you wouldn't have to access the ECU behind the passenger seat. It would be a simple process of elimination. (EDIT: But, of course, this is still no guarantee that there are no other wiring or wiring colour changes on your car. Oxygen sensor, Throttle Postion Sensor, Immobilizer and Start Relay wiring can also have variations)
That sounds right to me. Strange that the diagram in the manual shows it in the vertical orientation :facepalm: LOL It certainly is very detailed! Thanks, I don't need a personalized diagram, I appreciate it though. I'm sure I'll run into some issues when I swap the stand alone in lol
Now I'm confused. I was just reminded that the 5.2 exhaust diagram in the WSM shows no TC ECU for the bypass system, but has the Left Cat TC ECU on the RH side of the car (vertically oriented). Where is your Left Cat TC ECU (mine is on the LH side)? That's a third variation. My logic just went out the window. I thought they were still useful for diagnosing fuel/air issues?
Negative. Mine is like yours. The left bank TC sensor plugs into a TC ECU that's mounted on the left side of the engine bay near where the left bank O2 sensor plugs are.
All the main cat ones do is trip the Slow Down light if the cat temps get too hot. That's it. Very basic safety device. If you don't have cats, they are pointless. All you need to do is cap the bungs and install the Technistrada plugins and never worry about this unreliable finicky system again.
Irrespective of their original purpose, that is not to say that they can't be used as a diagnostic "tool" when they are working properly. There's a gentleman currently on the 360 forum with a misfire problem and he also noticed an SDL. Whether this is a finicky system or a possible clue as to what might be happening, that remains to be seen
My non-cat (from the factory) 348 still has the Thermocouples. They are installed to warn you if the EGT gets too high (usually if running too lean) to prevent the exhaust manifolds getting red-hot, prevent melting of pistons etc.
Pin 14 on the main computer 88 pin connector is the signal from the Bank 2 Cat TCU output. Wire colors are unreliable on 355. Hook up an ohm meter to Pin 4 main ecu, find which 4-pin TCU connector is connected to that signal. Then find whichever green TCU that connector is plugged into, and plug the thermocouple from the right side cat converter to the same TCU. The other TCU and its 4 pin connector is the one for the center By-Pass thermocouple.
I would guess the 348 system is calibrated differently than the 355 system, which is designed to warn of an overheating cat. Those temps are MUCH higher than normal EGT's. 355 SDL is tripped around 1,800F. If you're getting EGT's that high in a non-catted engine and trip the SDL, it is probably too late. If you're concerned about EGT's, I would install actual EGT sensors and gauge. I would like to do this given how important that data is for both banks. But relying on the factory SDL system for EGT's is like have a warning system that's tripped after the bomb goes off.
You may have a point, but the trip temperatures are only slightly lower for the flashing SDLs on the 348. 348 cat temperature: 1720F +/- 86F (938C +/- 30C) F355 cat temperature: 1778F +/- 86F (970C +/-30C) F355 Cat "operating" temperature 400C ~ 800C From an exhaust wrap website: ....the highest temperatures that an exhaust manifold or exhaust pipe should ever reach would be approximately 850°C (1,600°F). As a guide, metals will start to turn red at 500°C and be a dark cherry red at around 635°C (1,175°F). The hottest parts of your exhaust system will be either a bend in an exhaust pipe right next to the cylinder head or around the catalytic converter. Temperatures naturally increase as RPM or the engine work load increases. This is when the engine is consuming the maximum amount of fuel and producing the most amount of torque or horsepower. With no restriction, it would seem to be difficult to reach those trigger temperatures in a catless system. What are typical lean running temperatures at Ferrari rpms? Why did Ferrari fit the thermocouple system to the catless 348? Ease of production? (common wiring harnesses, etc?)
