I realize there is a lot of information on FChat regarding the 5.2 Cat transmitter (ECU) system and how to defeat it . My question is regarding my 1995 2.7 355. When removing the catalytic converters, most of the threads I have read paint a picture of the 2.7 system being fine with simple unplugging the "cat ecu" from the Motronic harness, removing the Thermocouple and being fine. I just tried this and wind up with the "slow down" lights happily glowing on the dash. I should note that the car already had test pipes when I got it and I was not having any slow down light issues. I just installed a complete Fabspeed exhaust and one of the Thermocouples wouldn't come out of the old test pipe so I wanted to take out the system rather than buy a new Thermocouple. I will simply put it back the way it was if I need to but thought I'd ask you folks first Did I miss something...like removing the bulbs or letting the leads hang in the breeze? Or is the 2.7 355 less tolerant of this heresy than the 348 is?
Try plugging the thermocouples back into the wiring harness, then use some cable ties to secure to a frame member, and you should be OK.
I plugged the good thermocouple back in correctly and I cut off the bad one and connected the two wire ends together (This tells the amplifier that there is a connection but obviously will never send a voltage to set off the light) and plugged it in. No lights on either side after a long test drive! Thanks.
"When removing the catalytic converters, most of the threads I have read paint a picture of the 2.7 system being fine with simple unplugging the "cat ecu" from the Motronic harness, removing the Thermocouple and being fine. I just tried this and wind up with the "slow down" lights happily glowing on the dash." I had the same experience and results. I'm not sure if that technique really works. I know for sure I have a bad thermocouple because I switched them around and got corresponding errors. I also tried cutting the tip and twisting the wires together and that still didn't work. Where exactly on the tip did you cut or does it not matter? I plan on running test pipes eventually and don't feel like spending $270 on a thermocouple I won't even "need." Any suggestions? Ken
Mine was a test...one one side I have a healthy thermocouple plugged in but wired up out of the way. On the other side I snipped a bad thermocouple near the connector and shorted the two wires together then shrink wrapping it, leaving it plugged in. Its been like this for over 3,000 miles and 90 days with never a slow down light or other issue. Its important to note that I DO NOT HAVE CATS! If you have a plugged-up cat then you may get slow down lights...and I don't recommend disabling this system if you are running cats. It sounds like if you shorted the leads on one side and still get the light, there is an issue with the amplifier(ECU) or something else.
If you cut the TC near the tip and there is a break in the wires upstream from there, it would explain why the TC is bad, and also why my fix didn't work. I suggest clipping very close to the connector.
This technique worked very well. I've been driving for weeks and not a single issue. The other techniques do not work and if anyone is running test pipes, a high flow cat, or simply dont care about your oem cats or you know you have a faulty thermocouple , then it would be best to do the same as I did. Ken
