Hi Guys, I had the 1/4 SDL on. I switch the units and the issue went to the 5/8 bank. Since the problem is intermitent and the light goes on as soon as I start the car... I felt like it could be a bad contact problem. I found a good thread about how to fix the 355 M5.2 Cat units and I did the same procedure.( http://www.ferrarichat.com/forum/348-355-sponsored-bradan/378429-thermocouples-slow-down-lights-related-cel%92s-how-conquer-them-3.html these guys did a nice job and research) Surprisingly! now runs well!! no more issues but... I don't really see any broken connection there and I don't know what I've fixed... I've just reweld the pins and connections. Do you guys know what should the input/output be? Ohms/volts? There are four wires on the unit but only 3 go in the ECU. Debbie
It would be good to have a little bit more information on what you did. In checking the schematic for the 2.5 system there is no connection from the thermocouple module to the ECU. The 2.7 system does have connections to the ECU. And going from memory, module has yellow and red T/C wires from the cat.converter and then probably a power wire and a ground wire and then a wire to the instrument warning light. In looking at my very poor copy, I can't read the wire colors but it looks like there are four wires coming out of the module (again 2.5 system) of which three connect to the body wiring harness. The modules are mounted close to the rear wheels and could get wet so maybe re-soldering the pins in the connector fixed the problem. The other module on the other side of the engine is wired the same with a different color wire going to the instrument cluster. Sometimes the Thermocouple fails so you could try switching them also. The thermocouple output is in milli-volts. Try Google for a type K Thermocouple chart. FWIW. Jeff Pintler 89 348tb (2.5), 86tr, 99 360 3-pedal, 05 S-160 Bobcat
Hi Jeff, Thanks to your quick answer. I couldn't sleep till I've checked the wire diagram. You are right, the Cat Unit doesn't have any connection with the engine ECU. It has four wires. The white is free/cancel. The black goes to the ground. The Yellow to the Dash SDL and the Red to the Ignition Key switch (fuse#6). I've just rewelded the inner pin and wire connectors. Now it just runs fine. Debbie Image Unavailable, Please Login
Hi Debbie. Of you search my posts you will find a thread where I thoroughly went through the sdl design and function and discussed the output voltages. I currently sti have tapped leads on the outputs on my sdecu do that I can monitor the transmitter outputs real time as I was trying to develop an alternative to the OEM ecu. The voltage curve has been plotted and I will find the graph for you the baseline voltage and cold start up is ,5v and the typical warm cat vomit age is around 2.7-3.0 volts. Sdl are triggered in the 3.5v area. There is a bias voltage present in the system and an unplugged cat ecu will show the motrinics 5v and trigger a sdl. Unplugged thermocouples will also trigger 5v output I had a faulty TC that in addition to a bad ecu created issues. I suggest and some may disagree, tapping your ecu outputs and monitor your ecu outputs real time to correctly diagnose your issues as opposed to swapping things around.
