348 thermo ECU

Okay, need the wisdom of the brotherhood once again.... Car is 95 348 Spider and in the shop for the major. I am told the thermocouple ecu on pass side is shot and needs to be replaced. This adds $1,000 to the bill!!! The tech said the light is intermittent so it's my call? Having new radiator on that side replace cause at plastic junction it has separated going with high flow aluminum one instead of OEM. Not sure if I'm 2.5 or 2.7 Motronic but, what to do??? Can it be unplugged entirely, do I get one online and pop it in? Or just bend slightly more forward and have them replace it? I'd like to be able to add to the 22,000 odometer this year and go on the FCA drives without worrying. Help

 

Unplug it and forget it.

 

+1

 

Is it the connection between the ecu and the thermocouple lead?

 

+2 Mine have been unplugged for years. Worthless piece of electronics. Oh, and I took my 348 through emissions today and the Techs didn't say a word about it.

 

so do you unplug both even if it's just one side that is on the fritz? Makes sense if you don't need one you don't need the other right?

 

No. The connection between the Cat ECU and the main harness.

Yes

 

Thanks as always !!!

 

Jevs posted an AWESOME thread on how to by pass those stupid things if you still want to monitor the cat temperatures. http://www.ferrarichat.com/forum/348-355/378429-thermocouples-slow-down-lights-related-cel%92s-how-conquer-them.html The thread is for a a 355 but it's still the same principals apply.

 

You can source them for less than that online... I just replaced one of mine which was the epoxy type stuff was pulling away.

I think it was a 8mm socket to undo it.. simple fix you can do yourself.

but I like the idea of just pulling them out.

 

If anyone has a known bad one for a 348 I still need one. I have one bad one. I want to install 2 bad ones so it looks original but is internally disconnected.

Thanks
Rodney

 

shoot me a PM.. I have a known bad one.

 

circling back to this... I have another bad ECU... and I'm cat-less so if I pull the ECU out ... won't that give me a CEL?

 

Deleted

 

On a 348 it won't light up the CEL, but it will store a silent code.

 

Hey Ernie..what happens when it does light up the CEL. Even after its disconnected? That's my current issue in another thread.

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If anyone's got a working 348-version cat ECU they'd be willing to loan to me for a week or two for testing, I'd be much obliged. I've been working on a microcontroller-based cat ECU replacement for the older K jetronic cars, and it might be worthwhile to have the same for the subset of motronic cars for which the stock cat ECU boxes are particularly expensive. To do that, I need to get my hands on a motronic-version ECU to verify that I can duplicate its operation and connector style.

As to the the OP's point about going on drives without worrying, since the ECU is the warning system for detecting an overheating catalytic converter, there's of course some risk involved in not replacing a failed one (assuming the cats are still present).

 

That I have no definite answer for.

I was made aware that on late model 348s ('94 iirc) the light will illuminate if the cat tcu is unplugged. My guess is it was a programming "update".

My 348 is a '90 and I get no light. I have been running with them unplugged for well over a decade. I get no check engine light but I do get a silent code stored (4121). So you may have the "updated" programming????

That is my best guess.

As for your issue, have you tried swapping the thermocouples side to side? Those do go bad.

 

I ran my 94 unplugged, (removed both probe and TCU from the car), for 4 years and no code. An occasional CEL flash or SDL flash and gone. I did get last week a 4121 with a MAF code as well. So, I reset it and see if it comes back.

If I have no cat, no TC probe, and the car is telling me that my cat is burning up, I am obviously going to ignore that code.

 

I can run ignoring the stored code if the darn thing wouldn't light and stumble the engine.

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You may need a frash set of EPROMs, and maybe even repin the T55 connctors??? Years back I had a bunch of weird CEL codes, swapped out all brand new sensors, issues persisted. Installed a fresh set of chip *presto* the madness stopped. Here are my diy threads for both.

http://www.ferrarichat.com/forum/technical-q-sponsored-algar-ferrari/351819-348-ecu-removal-chip-removal.html

http://www.ferrarichat.com/forum/technical-q-sponsored-algar-ferrari/444155-348-motronic-2-7-connector-harness-repin.html

But before you do any of that, have you tried swapping the Motronic ECUs from side to side to see if the problem follows?

 

Bringing this thread back...
When you guys say unplug them are you referring to the electric connection or removing the probe from the cats and leaving the electrical connections?
I'm assuming the later as this would make the car think they are installed and not overheating

 

Post 7 above.

 

So does this leave the CEL? I'm confused a bit.
Wouldn't unplugging the cat ecu cause the slow down lights and shut down that bank?
I have had intermittent 5/8 light and the last time the engine lost power. Trying to avoid that.
Please excuse the ignorance and I'm not home to start playing with it. Just want a plan of attack

 

Yes, a silent code (4121). Meaning the Motronic stores the code but does not illuminate the CEL.