Another 355 slow down issue

shout me if you want to borrow the ECU.

Just a thought but is the exhaust valve working correctly ? I bought the said ecu as my slow down light was coming on late last year after about 7 miles saw a used one on ebay and jumped in.
At the same time as this I was messing around with the exhaust valve and a cheap quicksilver box, I eventually found out that the valve was never really working properly so have replaced along with the vacuum solenoids and treated myself to a capristo.
I did pull the ecu plugs and check they were making a good connection but other than that nothing, no real reason but problem dissapeared, car has been fine all year ... touch wood ...
Try wiring open your exhaust valve (when the neighbors at work ) and see if that does anything as in theory your only going to be pumping half as much gas through the cats and senders.
A good run may also help cure the problem if you have not tried that already.
Its not something really silly like a short at the bulb end is it ?
Forgot to add Im at Brands Hatch area

 

Mine's a 5.2 .. I don't remember 100% but i may have not had a good SD lamp in at the time. Since then though i have replaced that along with the missing CEL bulb. But i have no SD issues now because i've used info from this site to formulate a voltage reducer that sends 1.5v per side back to the ecu (thanks Eric and Paul).

 

They are non-OEM cats, yes.

I haven't been able to verify in the exact way you've asked because I don't have anything to bung up the resultant holes in the cats, but I did do the 1.5v test using a battery on both sides concurrently thus eliminating both the cat ecu's and the thermocouples, and with that test the slow down light continued to flash.

Explain your thinking more on the ground issue please? I think the thermocouple is permanently touching the cat through the shoulder which buts right up to the threaded portion where it inserts. Thus if the cat body is connected to ground itself, then the body of the thermo must be grounded. What effect does that have? The thermocouple generates a tiny voltage across its terminals independently of any other power supply, so if it is touching the chassis earth then is there any problem with that as it's an open circuit so shorting should not be possible.

 

I was chatting with another owner today, and he mentioned that there is "too cold" as well as "too hot" and both will cause the light to flash. I'm not clear how "too cold" is calculated as the ECU would need to be able to differentiate between just started from cold and been running for ages and too cold. That leads me to consider that variables such as coolant temperature in the block or oil temperature together with things like engine load can be used. So I think a closer look at the OBD data (when my neighbour is at work ;-)) is in order. Perhaps there's another sensor that is giving a duff value from turn of the key.

The "too cold" thing rings true with the exhaust valve comment. Less gases past the cats when the valve is open. Although my money would be on a sensor as I don't think from cold the ECU will recognise an open valve as an issue - only when the car is warm and the cats are below temperature.

"too cold", perhaps the light should say "speed up" ;-)

 

I was just thinking out loud that perhaps the thermocouple was grounding out inside the cat and you were therfore getting too low a voltage at the ECU. What touched this off was your discription of difficulty putting in the one thermocouple. There would be a corresponding wear mark on the thermocouple where it shouldn't be touching anything. I realize that the body of the thermocouple is at ground but the probe itself should be isolated from ground I would think.

 

In light of your 1.5v test to bypass the thermocouple it renders the whole thing moot. However it the would suggest the problem is higher up the chain, connectors to ECU or any other input that effects the ECU-SDlight.
Does your SD light go through a start-up test and light up steady then blink? Perhaps the trouble lies there? Is there a fault condition on the start-up test that is documented somewhere?

 

I don't think that sensor system signals a too cold signal and even if it did your 1.5v battery bypass would be "Goldilocks" not too hot, not too cold but just RIGHT wouldn't it?

 

Now that i think more about my issues, i must have had my sd lamp inop at the time because my car would go into 'limp' mode. Your car do that? If not wow, must be something really wacky. As to too cool, never went limp when unplugged. If you're not limping, maybe just unplug the sd lamp, i don't think there's a cel for that, but there is for cel lamp inop.

 

It definitely checks for too cold, that's why you can't run test pipes on a 5.2 car without getting a slow down light. Of course, this is not the issue if the light comes on immediately as the ECU waits a certain amount of time before checking for low temp - to give the cats time to heat up.

 

Richard, I have a spare cat probe as well if you want to try, like the ecu it's used but believe it to be working.
Am around most of weekend in general if you want a spin out before it rains.
I will keep a look on here from time to time.

 

Yes, the SD lights solid when the ignition is on. About 1 second after the engine is started when all the other lights clear, the slow down light starts flashing.

 

Hmm, yes, if some other sensor shows the engine as hot when it isn't, then my 1.5v test should have cleared the light anyway.

 

Apart from rough idle, the car runs fine. Slow down lamp never goes solid, and it never cuts a bank out.

 

I ran test pipes for a couple of years on mine, and never had a check engine or slow down light. Talk about irony!

 

Not to sidetrack the discussion, but Pete, can you point to any technical references or examples of this? The Ferrari docs for the 5.2 based 550 Maranello say nothing about a Low Temp Alarm - only the High Temp Alarm and the High Temp Bank Shutdown.

Now it's true, the 5.2 based system has an open circuit detector which will trip a SD alarm if the thermocouple circuit is open.

 

Based on that type of behaviour I would suggest that the error condition is discovered during the ecu start-up and check out, The flashing may indicates a fault rather then a high temp situation and I'm sure there must be some documentation on this fault code somewhere. May need to talk with the dealer about this. Your manual has very little information other then the warning to get the car in for service.

 

Sorry, my mistake, it's actually due to the o2 sensors aft of the cats that trigger a CEL in the 5.2 cars, not SD.

 

Wow, how could you miss a flashing red light on your dash for so long? Are you sure you're not presenting a pseudo mystery? When did this corner come in to play? The corner you take when pulling out the drive? Backing out the garage? Straightening the wheel to back out? Corner? No offense.

 

I'm sure. I did explain this already. I had the airbag steering wheel raised high and in that position it obscures all of the warning lights a lot. In the straight ahead position I couldn't see any of them, and when turning a corner I'm normally looking out in front !

 

Yes, we're all sure it's not a high temp situation because it does it from a cold engine.

 

Update: The light is out.

I finally got chance to spend more time with the OBDII reader in a location where I wasn't disturbing anyone with a noisy Tubi running for minutes on end. As I mentioned before, there were no fault codes showing and the check engine / MIL light was off, but I pressed the reset codes button anyway, and the light went off instantly. I did this while the engine was running.

Took it for a drive, seems ok. Didn't come back, and I used plenty of revs to get the cats hot.

So I just need to watch it now and make sure it doesn't come back. It does seem as though the ECU remembers that it has had a bad state with regard to the cat temperatures. This is a bit unexpected given what I've read here and elsewhere but it's the only way I can explain it as I know the whole temperature sensing system is operating correctly, whereas there was a fault with the left thermocouple before.

Thanks for everyone's help. I hope I won't be back adding to the thread with a repeat problem.

 

Very glad to hear of the success.

 

Very good point for all of us to remember - after doing everything possible to sort out a pesky problem, and it's still there for no obvious reason, it's time to get out the OBDII reader/tester and reset the ECU('s). Hope this sorted it for you!

 

Fair Whack Mr! Glad you go it sorted and well done on your dogged determination!

 

hi

i seem to be having a similar problem but on a 456...similar electronics i beleive with similar shut down protocols.

what OBDII did you get to talk to your ECU. As this may be my salvation, as the ELM 327 (ebay special) i have does not recognise the protocol of the 456.

here is my tale of woes....if nothing else i know how irritating the damned issue is when nothing makes sense or changes anything!

http://www.ferrarichat.com/forum/showthread.php?t=360056&page=1


Any suggestions or comments greatly appreciated.