Intermittent start up problem

[non_linear]

Hi PS, always good to get a sanity check when it comes to the circuits!
I don't understand your question about the ignition voltage. Why would it not be the battery voltage?

[Penelope Stopit]

non_linear said:

Hi PS, always good to get a sanity check when it comes to the circuits!

Ok then
Everyone needs at least 2 pairs of eyes for reading diagrams

non_linear said:

I don't understand your question about the ignition voltage. Why would it not be the battery voltage?

If there is no battery positive connected directly to the ECU, ECU battery voltage doesn't exist and therefore can't be displayed as such by any software

What would be good to know.....

Is the battery voltage shown below really battery voltage or is it ignition voltage?

If the voltage shown is battery voltage, this tells us that the ECU had a permanent battery supply connected to it

---

I could be getting this all wrong

Just because I expect ECU diagnostic software to display ECU battery voltage it doesn't mean that the software shown is doing so, the voltage shown could be the battery voltage measured at a diagnostic socket or from a cable connected to the battery positive

[non_linear]

"If the voltage shown is battery voltage, this tells us that the ECU had a permanent battery supply connected to it"

If the ECU was permanently powered then it should be possible to connect the diagnostic software to it even with the ignition off, which you can't. I suppose it is possible there is a separate battery feed to the ECU just to keep the NVRAM powered, but there is no sign of this on the circuits.

I really believe MBU treated the NVRAM as a service item, with a service interval of ten years. I shall be interested if MBE reply but until then I have seen nothing to suggest the ECU is powered with the ignition off.

[Gladers01]

Penelope Stopit said:

non_linear said:

The drawings are complicated and I may be mis-reading them but I can't see how this is powered permanently[/url]

Verifying that you are reading the diagrams correctly

Have read through the very same diagrams many times

There is always the possibility of an incorrect diagram

You have very likely viewed the below image



Probably worth trying for a 12 volt reading at pin 52 of the Ecu plug with ignition on and off and alarm armed and disarmed, the inertia switch looks to be in series with the Ecu power supply and has a warning lamp (status signal) for the dash when activated, possibly the amber shift light assuming the drawings are accurate

[Penelope Stopit]

non_linear said:

"If the voltage shown is battery voltage, this tells us that the ECU had a permanent battery supply connected to it"

If the ECU was permanently powered then it should be possible to connect the diagnostic software to it even with the ignition off, which you can't. I suppose it is possible there is a separate battery feed to the ECU just to keep the NVRAM powered, but there is no sign of this on the circuits.

I really believe MBU treated the NVRAM as a service item, with a service interval of ten years. I shall be interested if MBE reply but until then I have seen nothing to suggest the ECU is powered with the ignition off.

Mmmm, was under the impression that the majority of ECU diagnostics needed ignition on for the ECU to start talking, have only been involved with diagnostics on vehicles that required ignition on, hence can't comment further

Anyway, this is a cracker of a topic, your investigations do seem to have exposed something new

[Englishman]

MBE haven't responded in a week, so I suspect they won't. Shouldn't be surprised really as the 941 series ECU's were introduced in the 90's and, as others have found, MBE are not really interested in answering questions about them after 25 years or so.

I have however found a little more historic information which suggests the DS1230Y chips have a limited life in these ECU's, albeit significantly longer than the chip manufacturers minimum data retention time of 10 years. So looks like, surprisingly, there was no attempt by MBE to retain the adaptive map data long term.

This site doesn’t seem to have been updated for quite a time but does contain interesting information about MBE ECU’s:

http://oddified.com/

This is taken from the section on MBE 941/970 ECU’s:

• These ecu's were also supplied to specialist car manufactures such as Tvr (usually anodized gold or blue rather than the normal black colour) and Noble. Those ecu's themselves are identical, but some of the software is bespoke for the specific applications with non standard inputs/outputs. The easimap software is not 100% compatible with some of them, but the files can be decoded and the maps edited. The Tvr ecu pictured on the left is really a regular 941 ecu (with idle control) but the software stored in the eprom is specific for the Tvr. Regular ecu's will use firmware versions such as 941BA463 where as the tvr uses a different numbering system such as 94110035. The eprom stores the firmware for the ecu as with a regular 941 or 970 ecu but the tvr version also stores the engine maps and settings. This means to change fuel or ignition maps, it's necessary to reprogram the eprom which cannot be done through the serial connection and easimap. The 2nd chip is a SRAM which is used to store adaptive maps such as fuel from the lambda inputs. These SRAM memory chips have an on board battery which normally fails after 15 - 20 years causing the engine to run very rough, often being blamed on the ecu being faulty. Replacing the chip cures the problem.

Bottom line, as non_linear has found and as known to at least some experts it seems, these chips can eventually drain their internal battery in this ECU meaning the adaptive map data may not be fully retained between starts. Probably means there are quite a few TVR’s out there recalculating their adaptive maps each time they start. Is this a major issue? Depends on what values are in the maps when the car is started. If zero’s, as on a map reset, or correct data is partially there from the last time started, probably not, but if random and the mapping firmware has significant work to do, it could mean rough running for a few minutes until the adaptive maps are recalculated.

If you are thinking of replacing the chip, I’d suggest you go for a DS1230Y rather than a DS1230AB (wider tolerance on operating voltage) and also with an IND suffix (wider temperature range) to ensure you don’t have problems in the cold. The number in the suffix is the access time of the chip, but as TVR originally fitted 200ns parts, anything equal to or lower than that would be fine. Looking at the Mouser Electronics website part DS1230Y-70IND+ would be ideal, just over £20 now.

[non_linear]

In my experience mouser can be rather slow in delivering components, especially as many are shipped from abroad. Indeed, if you put a DS1230Y-70IND+ into the cart and try checking out you will see international delivery is added to the final price which is around the £32 mark. I got my part from Farnell who have the DS1230Y-120IND+ in stock at just under £34 with next day delivery.

For anyone thinking of doing this I can't emphasise enough how important it is to use proper anti-static (ESD) methods when handling these components. Never touch the pins unless you have discharged yourself, never lay the component down on anything that can carry an electrostatic charge, so that is pretty much anything non conductive. Ideally you should wear an earth strap around your wrist connected to the cars earth (anything connected to the battery 0V). Keep the new part in the conductive foam it is supplied in until the last minute.

You can get the part cheaper from ebay but personally I would not as there is no guarantee that they have been handled correctly.

[Adrian@]

Hi Guys, I like the thought of the + ranges...I am sure I have read it somewhere, but what DIPn is the unit or is there a link to the one purchased please. A@

Edited by Adrian@ on Wednesday 8th December 19:42

[Englishman]

Adrian@ said:

Hi Guys, I like the thought of the + ranges...I am sure I have read it somewhere, but what DIPn is the unit or is there a link to the one purchased please. A@

The part fitted to the MBE ECU is a 28 pin DIP.

https://www.mouser.co.uk/datasheet/2/256/DS1230AB-...

[non_linear]

https://cpc.farnell.com/maxim-integrated-products/...

I believe Python Racing also stock them and I know Jody will handle them correctly.

[ukkid35]

I bought a couple of DS1230AB-200 about seven years ago, but I've never actually tried fitting one

Is it even worth doing so?

[Adrian@]

As for fitting it, I would say so, it holds the adaptive's, they will get learnt each time you run it anyway, but our Tamora is used all the time and is on it's second in 5 years (as I ran the battery down and recently whilst the clutch was replaced, which I think killed one) it starts from cold easier. A@