Ok, So this is an ongoing thread topic....because it is obviously and ongoing problem for 355 owners.
SDL means "SLOW DOWN" light on your dash.
CEL means "CHECK ENGINE" light on your dash.
You knew that already.
Here is my very small contribution, and some follow up questions for where this discussion seems to sometimes leave off. I am simply trying to clarify what I have learned so far.....regurgitating info to keep the knowledge base growing...and maybe get some more clarification to all of our questions. This is a soupy science, this CEL and SDL stuff....ambiguous at best. It baffles some of us. Me for example. A new owner of a 1997 5.2 F355....my dash, well it looks like damn christmas tree. The green light is fine. I like that one. The red and orange ones....my least favorite of the light show.
What I have found through researching this and other forums (4) and the faulty CEL and SDL lights tend
to be false, and that the problem is with the sensors/ ECU's usually
. As if to say the warning system is failing but there might not really be a problem with the cats or bypass. Sometimes the sensors are all working properly, and there IS a problem with your cat(s) or other systems. Soup.
Other scenarios....they are in the dozens: A virtual rubix cube of conundrum.
1.) There might be an ECU that is cracked (black epoxy ones usually, as opposed to the newer green epoxy ECU's). SOMETIMES you can simply clean the connections to the ECU's and thermocouplers, and the problem will go away. Someone mentioned an "earth strap" they cleaned and it solved the problem when they cleaned this all other connections (what is this part? couldn't find it in the shop manuals. earth strap?)
2.) Sometimes moisture situations (car washed, rain, fog) will make sensors go buggy. (steaming cats?) Sometimes it is just one ECU. Sometimes it is two ECU's and one thermocoupler, or just one thermocoupler. HMMMMM soupy science again. Dealerships suggest replacing all 3 ECU's and all three thermocouplers (USA version = 3 of both. 1 for the muffler, 2 for the cats, if I am not mistaken.)\ Pricey. $1850 with labor. (my quote from Ferrari)
3.) Sometimes your cats ARE actually bad.
4.) Sometimes an ECU or sensor is going bad...on and off, on and off. What does it mean?!?*%$*!!!!
Here are scenarios for CEL and SDL lights:
here we go...
1.) CEL always on, even at cold start up. ON ALWAYS.
2.) CEL on sometimes. comes on, goes away...maybe it flickers.
3.) SDL (Slow donw light) is blinking always, even at cold start-up. Always blinks. Always.
4.) SDL comes on at start up, but goes away after warm up and with spirited driving. (F 355's seem to love being pushed harder. It sometimes clears CEL and SDL dash lights.
5.) CEL off, but SDL on at start-up.
-Here is a small piece of knowledge I picked up today. IF you have faulty ECU.... with SDL blinking at cold start-up, AND a CEL at cold start up (which stays on always).....AND you have a USA F 355 version with 3 thermocouplers and corresponding ECU's....then you might look at the muffler ECU first, or in other words, the one which is NOT associated with the cats, whatever it may be called. I read that this ECU will, if bad, throw BOTH a CEL and SDL at cold start-up. I have this problem. This is where I am going to start, in an attempt to save a LOT of money.
-Another one: Twice I read that is was simply a bad spark plug. Changed the plug, solved the problem immediately.
-Some people with 2.7 can swap ECU's around and ISOLATE the problem.
-People who disconnect the ECU's (one or both etc) STILL had the SDL light on because disconnecting them will automatically throw the light.
Here is what my dealership showed me; here are my codes: (See picture)
I plan to buy a new ECU and start there. Where it goes, I will share...
Any thoughts? It says RIGHT HAND bank on one code. Hmmm. Maybe that will help isolate the faulty code, if thats what it is. The dealership told me that it is probably a faulty ECU, accounting for BOTH my CEL and SDL at cold start up.
Anyone have these same codes? Did you ever isolate what the problem was?
I am going to see what lights up on my dash after the new exhaust is in. The service manager told me that SOMETIMES a new exhaust can eliminate an SDL, perhaps because the pipes are breathing better...
Thanks guys. Hope I helped someone, and hope someone can help me isolate where to start so I can save a lot of money. I just put a lot into a major engine service and new rear axle boots....and tires...and Nouvalari exhaust since my headers looked fine. $ cha-ching. Ouch.