"Slow Down" Lights coming on at same time - always

Well....once the engine is started it's not "normal" for them to come on at all

They work independently--each bank has it's own "ECU". They fail often and give erroneous readings. They should come on together for a few seconds as a self-test when the key is turned to position "II" (BTW there is no position "I"), but to come on together at the same time while driving is a bit suspicious. Are the thermocouples actually inserted in the exhaust or have they been removed and tied to the chassis?

Do they come on exactly at the same time or approximately at the same time?

 

Yep.

 

Hi Joe, these lights re a PITA .... often caused by bad contacts .... clean then ... and hope it helps ...

 

take out the instruments and have a look how those 2 lights are connected. normaly both lights have to go on when ignition is on and will go out after the engine is running, may be also when only ignition is on and engine is not running after a while they will go out, but don´t know this

 

Yes, another part of this car that sucks. These ECU's are glorified on/off switches. They run about $600. Very pricey for a light switch. I've replaced both over many years. I've considered tearing one of the old ones apart to see if I can fix it and re-seal it. Thee problem is the backing is like an epoxy. It originally sealed the unit but it shrinks, cracks, and allows moisture inside.

Many people disable, or remove these especially if they have modified the exhaust.

These sensors are for detecting when your cats are overheating. If you're not aware enough to know that your cats are clogged and getting hot, you probably shouldn't own this car.

 

Disconnect PLUS from battery, connect PLUS cable 20 secs to earth ... Ecu's are now reset. Connect ....

Should be no more lights ... normally.

But DO read this thread ... (made for 512TR, hope it brings you something for TR) ... or just a info ...

 

Mel that only works on the 512TR. OP has a 1987 Testarossa.

Sounds like the self-test function is not working on the 7-12 ECU--not uncommon. The 1-6 is working correctly (at startup at least). As others have said, it's important to know if you actually have an overheat problem (blocked catalyst) or an indication problem. If indication only you'll have to decide how important it is to repair. If you don't have hollowed-out cats it would be best to have the system operational or monitor your temps frequently (IR gun for example). The overall system is simple but the CAT ECUs are crap.

There were three different iterations of the ECU during production and even the last ones were unreliable. Start by checking the connections at the ECUs--there is a rectangular panel above your cyl. 1-6 (RH) fuel accumulator. Remove two 10mm (wrench) bolts and unclip the large wire harness attached to it. Carefully withdraw panel to access connections.

Each termocouple will have two wires going to their respective ECU (one wire is red, the other yellow). On my '88, at the ECU end one thermocouple has a green band, the other a red band: green=cyl. 1-6, red=cyl. 7-12. My (2nd design) thermocouples have two bullet connectors that plug into the female plugs on the ECU (1st design screwed in (I think). Also on each ECU is a four pin plug (only three pins are used)--these are also color coded red and green. There should be a black (ground) wire for each. Next, there is a green with white trace wire that connects the two ECUs, then goes from the 1-6 ECU through connector C7, to the fuse panel "w" connector, terminating at fuse#22. Finally, there is a red wire (on the 7-12 ECU) and a green wire (on the 1-6 ECU) that go to each dash light & the warning buzzer.

I would start at the ECUs since they are easier to access. Make sure your connections are correct and serviceable (not corroded). Moisture was a problem in the engine bay, the third design finally incorporated weatherpack connectors to try to make the system more reliable. Check the thermocouples at each end. Check the ground. Let us know what you find.
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The Tubi shouldn't make any difference, the thermocouples are between the Tubi and the manifolds. If your temps are actually high it's because your cats are clogged (the honeycomb matrix inside breaks up over time and can obstruct the airflow).

 

Maybe, unless both are clogged (which your lights are indicating is the case) so there wouldn't be any comparison left to right. The IR gun I mentioned should give a good indication after the car has been driven, but honestly the best way is to physically inspect them. Here are some (lousy) shots of my pre-cats for reference. Sorry I don't have photos of the inside of the cats themselves.
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That is correct -- that line from the warning light ECUs is not used.

No, it should not. Is the (annoying) "buzzer" that normally comes on with either of those lights still connected?