Slow down light stumping me.

I have used off the shelf voltage amps in my car and they start at .2v cold and throws a sdl until the MAIN ECU which controls the sdl, sees what it likes as the cats warm up. The OEM SDECU start at approx .5v.

You can get sdl at start up due to faulty components, either TC or SDECUs.

 

A stand alone system is just that. The SDL is not more stand alone than any other input device into the ECU.

 

Whatever you say Dave. Semantics aside. There are no other input parameters for the SDL system other than the outputs of the Thermocouples. It's a simple exhaust gas temp system used in many combustion engine applications.

There is no O2 sensor involvement. As I said, if there is a particularly rich condition on one side that may be creating a hot cat that is triggering an sdl then you could say that the O2 sensor is involved as it is involved in determining the mixture that is creating the rich condition maybe. But the outputs of the O2 sensors do not directly control or modify the SDL.

 

Semantics? You mean like GTB vs. Berlinetta?

 

Both suck Spiders FTW lol


The 2.7 & 5.2 are totally different. The 2.7 has if I remember 2-3 sets of maps. The 5.2 has 3-4 depending on what parameters the ancillary sensors are reporting it will switch accordingly to the appropriate map. Water temp, Coolant temp, Exhaust temp. I would need to check my notes but I did give up on both of them for lack of duty cycle.
The SD2 should show all the MAPS switching points, I hope


Yeah it's knuckle scraper ecu's foo sure





BTW you ever met my cousin Larry ?

l
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I don't know where exactly the TC-s are positioned on your straight pipes but, if they are closer to the muffler side (like on my factory pipes, non-cat 348), they might be seeing "colder" exhaust temperatures. Perhaps moving them closer to the exhaust manifold side would keep them warmer and solve the SDL problem. On the non-cat 348, the TC-s being far from the exhaust manifold does not cause SDL problem as it uses different TCU-s which, I believe, are calibrated to such TC positioning (and the EGT they see).

 

Thanks for the update Mitchell. Glad you got it figured out.

 

From the wsm I agree with that statement.

As with most but not all faults tend to go through the main ecu.

 

No I dont think you told us straight pipes, until now.....

 

Oh, so yours is the car that stinks

 

I do not get it.
If your TC's are not connected to the exhaust system, then they are too cold to produce above the .5V threshold, right? Ergo SDL.
But if that would have been the case, then a stock exhaust/cat system would start with a SDL as well until the system was warmed up a little. Which it doesn't.

If your TC's do not produce .5V , then it sounds like they do not function correct anymore. Mine produce (amplified) .6V from cold.
And if your SDL comes in after 20 mins of driving, after everything in the engine bay is at least 125 degrees, why would that be the moment for the system to register that the voltage is too low?
Should have gotten the SDL from the cold start in that case...

 

Mitchell, why not install some Goth no-cat TCUs.... or the diode/resistor plugs shown in this thread:

http://www.ferrarichat.com/forum/348-355-sponsored-bradan/538719-simple-2-7-slow-down-ecu-replacement-only-no-cats.html

Here's my simple version (no external wires)...
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Never heard of that, but what you are saying is that an engine idling for an extended period generates an exhaust temp of less than 250 degrees, ' cause anything hotter would increase the voltage above 0.5V.

So, do the SDLs go out when you drive the car?

[edit] I did a little search of my own and I think it's a stretch to blame this on test pipes. Seems the same problem has been reported more than once on cars with cats.

 

In its case, it would start by changing the female plugs of the cables that go to the ECU. It is the simplest and probably decisive. I have had exactly the same problem. I have built power supplies for 3v with no result. Until I connected them directly to the cables, without plugs. No more SDL since then.

 

The issue with test pipes and sdl revolves around the bypass TC in a 5.2 car. Apparently in some exhaust config with test pipes, that location doesn't get what the ecu wants and throws a sdl. Skipp had this issue and with a bunch of variants before, solved it with goths fixed output box as suggested above.

My understanding is that the cat locations should still function normally, test pipes or not. The exhaust temps sensed by the TC should fall into range.

If it was my car, I would back probe or tap those outputs and drive around with a dvom and watch the voltages that are being sent to the ecu and replace/ swap tc and sdecu until they are correct. It really is an easy way to diagnose and fix these things.

I'd get goths fixed transmitter for the bypass location.

 

I believe Eric C was successfully running test pipes in his 5.2 car. Skipp not only had test pipes, but Tubi headers and Capristo bypass valve and if I recall correct, he was not getting SDL's - only the CEL with P1448.

Seems totally different to the current issue Mitch is having.

 

One problem I have is that in the original post Mitch said the SDL came on after an extended period of idling and that the TCU output was 0.5V. That would imply that the exhaust temp was 250*F or less. Seems unreasonable. Anyway, I've made my 2 comments. Nothing more to add. Typical guessing game.

 

I don't have cats and mine does this sometimes.

I tested all the parts as described in another thread and all passed, sometimes I get a flashing light when the engine is cold right at start up, other times it's interminate like aloose wire or conection because the SDL flickers.

It did the flicker today when I slowed down for some construction, it flickered, flashed then after driving away getting me speed going the SDL goes out. What a pile

 

That is good news. My 5.2 likes to light up the SDL from time to time when it is stone cold. Then after 15-20 minutes of driving.....it disappears. It isn't consistent but it is annoying. I have catalytic converters on the car so something else is causing the ECU to activate the light. My guess is a connector issue, broken wire or a dodgy TC but it doesn't happen frequently enough to spend the time to track it down. Of course if it started shutting down engine banks......that is an entirely story.

 

Final update? You are considering this problem solved, Mitch?

 

I like that.

How did you insert the diode?

Some more diy detail would be nice.

 

Ha! Spoke like a true Stooge