Here is one interesting issue... I just replaced my front bumper, myself of course, after some damage was done. Got it through the shop and looks great. Put it all back together, all functions and looks great. Take it for a ride, put the a/c on and about 5 min later, the slow down light comes on solid. goes away when accelerate..... Well after some trials, it appears to come on when I hit my brakes harder than a normal stop. It comes on, then it goes away like a wire is touching ground, shorting, etc as I start to brake hard... A/C was just a coincidence.. Is there anything up front that would cause that? I did not think so, but I will post on the forum. Nothing else has been changed, I have new cats as of 500 mi ago, and never had said problem.... It is only momentary and comes on when I brake..... so, how many dangling wires are in my car and what are they, that would trigger the SD light.. ohh and one light ( 99 F1 355)
The cataylic converter temperature ecu's are located in engine bay, just behind the shock towers. If you follow the wire comeing out of the cats you can see if it is touching something and causing a short.
Sounds like your cat ECU's are going. They are in the back of the car (one on each side, for each cat). They are about 2 inches by 6 inches or so - check and see if there is cracking around the inside rim where the inside part meets the outside shell. If there is a separation there, then it will allow moisture in and that can cause problems. The higher heat from the new cats (if they are not factory) could be a factor. On my 355, I had 'slow down' light problems due to the cat ECU's going bad. Ray
The ECU is getting faulty on my 98 model (light occasionally blinks at start up when cats are cold). How do I tell which ECU to replace since there's only one Slow Down light??
Unplug just one. If the light doesn't come on then you got the correct ecu. If it comes on then you know it's the other one. Just so you know, when you disconnect the cat ecu, the Motronic ecu will store a silent code telling you that you don't have communication with the exhaust ecu's.
Hey Ernie, my car is a 1997 F355 and it has three thermocouple ecu's. one on the drivers side for that side and two on the rear of the passenger rear wheel. Now my question: Would a sticking bypass valve soleniod cause a P1445 Vescovini code? Since the thermocouple is not getting hot when it is supposed to? BTW I think my solenoid is sticking because I let my friend rev the engine and the bypass opens very slowly and I still get the P1448 code that says the bypass circuit is malfunctioning. Any help is greatly appreciated!! OZ
Hear is what I know. The slow down light comes on for three reasons. 1) The operating temperature of the catalytic converter has gone over the maximum range 2) The cat ecu is faulty 3) The thermocouple is faulty If the cat temperature doesn't go over the maximum range, then there is no reason for it to throw a slow down light. However, if you get a check engine, and it gives you the cat ecu code, then it is telling you that the Motronic ecu is not getting a proper signal, meaning that either #2 or #3 are the problem. Other than those reasons I don't see why a sticking bypass valve would cause a slow down light to come on. I can see a check engine light coming on because of a sticking bypass, but not a slow down light.
I had same problem (?) when I got a traffic jam (over 2 hours in summer time) a few years ago. But once went back to normal drive, slow down light came off and no more...
