And another SDL posting...

I could not agree more. The TCU's are a long known issue.

 

I didn't see this in any posts but it is possible that the OBD II connector on the monotrinic need to have the pin 4 mode done. That is, if the pin 4 slot is empty, a pin needed to be inserted and a jumper wire placed between pins 4 and 5. Otherwise, the scanner may not connect to the monotronic.
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Per John's post - here is the OBDII recall document.

This might only relate to NA - I'm not sure if it differs for Euro cars or not
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Do you have an exhaust bypass ECU? Its the same part number as the SDL ECU. If you do, you can swap the ECUs and see if it trips a bypass malfunction OBD code (1448 i think?) That will confirm that the ECU responsible for the SDL is malfunctioning. If not, you can't swap side to side since in the 5.2 motronic, there's only one SDL for both banks.

 

He does not - it's a Euro car and they don't have them.

 

It is my understanding that prior to 2001 there was no 16 pin OBD plug in euro like our US cars have. The signal , ground and DC wires are there but they require a different adapter and reader. I believe this is what the OP is working on getting sorted now.

I have two working, black potted SDECUs. While they may be problematic at some point just because they are present doesn't mean that is the issue.

I have a logging DVOM and have also watched the SDECU outputs with a standard DVOM and have seen the spiking, intermittent behavior real time. It is pretty easy to diagnose if you do what the OP did and monitor the outputs.

If he does have a retained code then clearing it may solve this SDL issue but it doesn't resolve what caused it to begin with. It seems he has a handle on the diagnostics and if he does clear it and resolve the current problem he will be able to track down the fault if it reappears.

 

Thinking here.

You don't have the third BP SDECU that NA cars have, but does the electrical harness have the connector on it? Did they make a different harness for each market?

If that BP connector is there, right side location, is it possible that somehow your right SDECU is plugged into it rather than the correct Cat connector?

On NA cars they are identifiable by the color of the boot and clip on the connector. If you look at the left side one, the right side matches that and the third one is unique. I've got pics of them around if needed.

Just a thought as it has been inadvertantly done here in US and caused head scratching SDL issues.

 

There's no guarantee you'll get anything useful from the scanner in terms of fault codes. On my car, when it threw a flashing slowdown light, there were no error codes stored. This I believe is because the cat temperature monitoring system is not fundamentally part of the engine management system unlike, say, the lambda sensors.

During my investigations I eventually diagnosed a faulty thermocouple. But what threw me off during that process was that the motronic does indeed have a memory of sorts such that in certain circumstances even if everything in the system is fixed it will still flash the slowdown light until you reset the error codes (even if there are no error codes present).

The first OBDII software app I used would not let me reset the codes unless any were actually showing. Thus I could not seem to find the cause of the problem. The second app I tried would allow a reset regardless. This was important given how the system works and it was that which helped me diagnose and fix the problem.

Note if you don't get any codes, one test you can try is to start the engine and then pull the connector off the mass air flow sensor. Leaving the engine running, plug it back in and remove it a second time. This will cause a pending code to be generated which can then be cleared easily. If you don't get this pending code then your code reader isn't working properly.

In my opinion the most likely difference for the two motronic types is different emissions standards.

 

I had a different experience. I had two bad (black) ecus and one functioning (green) one. The green one belonged to one of the cat thermocouples (i think the left one) and the other two were on the bypass thermocouple and the right side cat thermocouple.

As a result, i had a sdl from one of the black ecu and a bypass valve obd code from the other. A couple of quick swaps of the ecu connectors, and checking for obd codes and sdls confirmed that i had one functional and two broken ecus.

I'm pretty sure there is no OBD code related to cat temps, which are measured by the thermocouple and "interpreted" by the cat ecu. If the temps are high, the sdl flashes. If it is excessively high, then the car goes into limp mode. To my knowledge, they should not trip an obd code.

The only OBD code my car had was related to the bypass valve but after hooking up the good ecu to that thermocouple, the code never reoccurred. The sdl , however, persisted until i replaced the other two ecus. They then disappeared without needing to clear any codes. I'm not sure how clearing a code would affect sdl. Is there any evidence about this?

In your case, without a bypass ecu and the one sdl referring to both sides, it would be more difficult to isolate a bad ecu. Thats where the electronic diagnostic tools may be quite useful.

 

Yes I agree there are no codes relating to cat temps.

The only reason I posted about codes is it will help him in general understand whether his new code reader is working or not, since he ordered one and wasn't sure whether it will work. If he reads the codes and there are none returned, he won't know whether the codes were read successfully. I never trust a system that says "no codes found" until I know that when there is a code it can be read, if you see what I mean.

 

There are codes related that cat temps and they are specific to which side. See below OBD list for PI 445 and 449.

Having said that, you don't always get a code with every sdl. I believe that in some situations like my blinking sdl as a result of low starting voltage, it doesn't throw a code just a warning. Also, there isn't always s CEL with the temp codes. You may be confusing CEL and these codes.
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Now that you mention it, my memory about this is returning. Its been more than 5 years since I've thought about it but you are correct. I do now recall there was a 1449 code in addition to the 1448 (bypass valve) code during the time my sdl was acting up. Cel wasn't tripping though. Just a pending code. Such a wealth of information shared on this site.

 

DR Bobs comment on the connectors being swapped on the right side is something to check. Mine were swapped after a major service. Worth a look to see if you have a spare connector back there.

 

FWIW - my car (with my scanner) needs to be started to connect and read the codes...

 

I think your car is a Euro. These have no OBD connector. That 3 pin plug, is for an SD reader.

 

Here is that post from Eric. I have no idea about this procedure and if it works or not. Hopefully some other euro guys can chime in.

http://www.ferrarichat.com/forum/138424319-post2.html

 

On my UK spec 355 (which also does not have an OBD connector as standard) I use a bluetooth scanner with a cable built to the spec you mention, specifically this one:
https://www.amazon.co.uk/gp/product/B00DY3EZSI

Sorry for some reason that amazon link is being translated into some shopping link but if you go to amazon dot co dot uk slash gp slash product slash B00DY3EZSI then you'll see it.

I don't have access to it immediately but can get it later and describe the connections to you if you need to compare. The problem is usually the protocol. I use OBD Fusion on Android and can tell you for certain that one of the protocols it supports works properly.

I'm pretty sure it's a 10.4kbaud connection, but I can't remember which one. Unfortunately I can't just connect it up and tell you as my car is currently in bits while I do an engine out service, so not in a working state. On the assumption I'm right that it's 10.4kbaud, there are only three options in the app - it's either SAE J1850 VPW, ISO 14230-4 KWP 5 baud init, or ISO 14230-4 KWP fast init.

 

KKmoon Mini V2.1 OBD2 Bluetooth Interface Auto Car Scanner Diagnostic Tool for Android | kkmoon.com

The amazon link was for this.