Testarossa Cat Temp (SLOW DOWN) Circuit Diagram???

I just got a 1990 US Testarossa, and was very happy to see that the SLOW DOWN lights would self test at each start-up, meaning no previous owner just disconnected the things. But after a few drives I started to occasionally see a little flicker (not a "flashing") in the 7-12, and after tons of reading here and elsewhere was getting ready for lots of trouble shooting (really hot and bothered vs. bad sensors, etc., etc.).

While doing some research prior to really tackling this, one post caught my eye and made me stop and go back and check and now BOTH of the slow down lights don't self test, which makes it a little hard to just do some quick-and-dirty swaps. It's a little hard to justify the cost of getting another "Catalytic Converter Control Unit with Multi Plug Connector Water Proof" on the off chance they both suddenly, simultaneously decided to go bad.

So my _real_ problem here is that I can't find any info or wiring diagram about the cat temp circuits at all in my service manual. The manual came with the car, and does include the D61- section all about my Jetronic w/Lambda and even a wiring diagram for that, but nothing the cat temp circuit. There’s even a physical layout of the sensors and control units, just no wiring at all. And there's nothing in the wiring diagrams of Section I (not even on the dash lights page).

I really want to troubleshoot this, but it's really hard doing it blind without knowing the wiring/connector layout. I'd love to make sure that the control units are getting the power and ground, check the dash lights by forcing them on from that connector, etc., but I've got no pin-outs for any of this stuff.

Is there some version of the service manual that actually includes this information, or am I just missing it in mine? I've seen inexpensive CD's for sale on-line, but didn't want to spend the money if it's not covered.

Also as part of my troubleshooting, does anyone know what type of thermocouple is in there (K type, or whatever)? (thinking ahead to possible diagnostics and alternatives to the controllers, if needed)

Thanks in advance for any tips on finding the wiring info!

P.S. The other thing the service (and owner's) manual completely ignores on my car is the automatic shoulder belts, which I'll also have to be working on at some point.

P.P.S. Sorry if this is a repeat question; I have read lots of posts here and elsewhere and haven’t seen this covered.

P.P.P.S. Yes, I do understand the risks of ignoring this problem, and will be doing plenty of non-contact and contact temperature measurements of the cats, pipes, etc. Just want to start by making sure there’s even a light to look at before starting it up.

 

Thanks a million for the quick response, Steve, that's exactly what I need to get me started on this. (contemplating digging into the guts of this potted ECU and what it does will have to wait until I really know it's failed...)

And so these wires continue on to some connector in the passenger footwell, as you mentioned here?
http://www.ferrarichat.com/forum/showthread.php?t=236073
Just trying to arm myself with as much info as possible, in case the chase gets weirder and I have to follow things further down the line.

Looks like the 509/88 manual is exactly what I'm missing here, and I'll try to track one down. Does it also show some of the nice details that the regular manual shows, such as location of important components, or is it just straight wiring diagrams? The little reading I did on it seems to suggest that they used this as a mechanism to cover some of various updates in the later cars.

 

Working on the electronics is what I was hoping I could bring to the table when I bought into the idea of getting a Testarossa. The systems themselves just aren't all that complex (famous last words), so it's really the maddening connection and grounding gremlins that are out there to drive you crazy.

None of these wiring manuals on E-bay at the moment, just ones for the older or Euro cars, but I'll keep looking. There's at least one cheap-o CD out there, but I don't think it covers this specific manual, and likely not even the Jetronic w/Lambda info that's already in my service manual.

I understand that this will also cover the automatic seatbelts on my car? But if this has only the wiring, what service manual actually covers the mechanical components of that system? Some previous owner has disconnected them, and while the wiring will help me figure out how they did that, I'll still be stuck with the fact that they probably did it for a reason!

Thanks again for everyone's help here.

 

Wow, thanks to everyone for helping me out here.

With the great tips I was able to confirm that the lights and power are fine, and that somehow in the course of a week I went from two working cat temp control units to no working units. Guess that's my welcome to the world of old Ferraris. Even got both units out on the bench to test them at different supply voltages, in case that was the bug, but neither function. One draws ~40mA, one draws 0. Doubt trying to dig open those potted things is going to get me anywhere, but I'll look. Otherwise I'm seriously thinking about just making my own units with equivalent functionality. Wouldn't be that hard to make something that would do the job, but would be harder to have something I half-ass threw together survive the harsh environment back there.

The thermocouples still seem to be in good shape, and I was reassured to see only about a 10 deg C difference between the systems about 60 seconds after cool down from my drive home (still assuming K-type thermocouples, anyone know?). Going to temporarily strap in a two-channel hand-held meter in the back and have it record max temps for both thermocouples as I drive. Not a real warning light, but at least I'll know (after the fact) if one side or the other is going crazy, and even might be able bridge the high-temp buzzer over to control the original lights.

Thanks again!

Oh, my buzzer didn't go off when I forced the SLOW DOWN lights on. Does this mean somebody disconnected it? Is this something that I'd see under the oil pressure circuit in my older wiring diagrams?

 

I guess with that many copies out there it would explain why the Testarossa is such an undervalued Ferrari.

To my credit, I'd just hoped that there was some more "logical" explanation why these two things failed so quickly together, like common power connection, or common hot side of the indicator. I've got enough experience with funky old '80's electronics that I should have known better.

But with the cost and fragility of these ECU's, I'm still going to be suborn and try to come up with another option. Even a cheap-o dual hand-held meter can throw out a buzzer for high temp, although out in the back it might be a little hard to hear. And a meter would have an actual display of the temperatures for diagnostics. With the proper thermocouple extension wiring you could put that up in the cabin as well. The main problem with a true replacement would be survivability in the current location, and I'd want to maintain the same self-test indications at start-up. Going to look at some off-the-shelf industrial module solutions first and see what's available, and in the meantime I'll have to dig into those potted units anyway if only to retrieve the stock wiring and connectors. Maybe if I can still identify some remnants of what's in there it will help refine my current mental design for a from-scratch replacement.


And thanks again, as I'd got two birds with one stone in that picture, because now I know where the seatbelt controller is. I was planing on getting it to Ferrari, but wanted to know how to reconnect it so I don't get charged for them to figure out how the last guy had disabled the stuff.

The fuse box is pretty high on my list of to-do's (only outside evidence is on the A/C pin and one of the fans), so it'll be fun to dig through that part of the car. Wonder why the thing that totally looks like a buzzer (#13) isn't actually the buzzer, though it's probably just indicating the component position on that rail for different versions. The other buzzer (door open) is already changing its tone quite a bit under different loads to prod me on to hunt down fuse box and other voltage drop issues.