Slow down

Not necessarily. My bad cat ECU merely caused the light to come on prematurely.

 

My question is unrelated to the cat ECUs (which I'll guess one or two have failed). But what was the modification to your Y-pipe? Have the cats been gutted from it? Did you also replace the one shown in your picture with an aftermarket piece?

 

a bad cat ECU.. and or bad thermo wires.. to my understanding.. will not put the car into limp mode/solid SDL. instead only a flashing SDL..

the fact that the car is indeed going into limp mode... something is happening more then a failed cat ECU etc..

in fact.. the system may be doing exactly what its supposed to be doing.. something is heating up enough on that side... to trigger the solid SDL limp mode..


how were your coolant/oil temps etc..

possible as some do.. get the car up and running.. and use a thermo gun.. once limp mode triggers.. see if one side ( headers, cats) is hotter then other etc..

or indeed, your pipe looks like its been opened..?

also is you Bypass valve working properly..? if its not.. the primary cats and probes may be seeing too much heat.. since nothing is passing through the ypipe etc.

 

My bad cat ECU caused a flashing light and, soon after, limp mode.

Pulling the plug out of the ECU results in a flashing light but won't shut down the bank - maybe that's what you were thinking of.

 

I would suggest some further diagnosis first. Use a laser thermometer to compare the temperatures of the primary cats when the slow down light starts flashing and the bank goes on to shut down. Are they both the same temperature? (if you don't have a laser thermometer, in a dark garage you may see one cat glowing, but re the thermometer, buy one - they're very useful). If yes, swap the cat ECU units over, does the other bank now shut down? If not, put the ECUs back and swap thermocouples (cool engine obvs). Does the other bank now shut down?

Don't drive the car with a bank down, amongst other things you can break the prop shaft.