John Speake

JDSPorsche now repairs LH ECU's as well as LH hot wire MAFs. I've just added a preliminary version of the downloadable FAQ's with pictures for the LH ECU repair section. Click on the link to FAQ's at the bottom left of the main LH ECU repair page.

They can be viewed at www.jdsporsche.com

I hope you find these FAQs interesting and helpful ! Any constructive criticism and comments will be appreciated.............

Please add any such comments to this thread so that others can share your views.

The US price for LH 2.3 ECU repair (1987 models onwards) is $550. The current price for LH MAF refurbishment is $350.

I hope soon to be able to offer a loan unit located in the USA, to assist with fault finding. Such an arrangement already exists for the MAF.

Thanks Randy V. for allowing this mail !

GoRideSno

Wow, a new "tile". And I thought the rpm signal output device you made me was cool. This really makes me want to know more about electronics. Keep up the good work!

Andy K

John Speake

Glad you like it !

User 4221

John,

The tile appears to be AL02. Is this the case? If so, did you re-design it with Alum. Nitride?

Not trying to steal any IP, just trying to understand the physics of LH failure.

Thanks,
Scott

John Speake

Hi Scott,
The original is a thick film hybrid, which has some kind of ceramic subsrate. I'm not a physicist so I don't know exactly what it is, but I believe you are correct about ALO2 Onto this substrate are printed (silk screened) carbon inks for the resistors, and conductors are silver (maybe vacuum deposted, I'm not sure.)

Then "naked" integrated circuits are directly wire bonded to gold pads attached to the aluminium tracks. There are also layers of insualtion where the silver tracks ahve to cross each other because there are only tracks on one side of the substrate. The thick film technolgy was prettty state of the art in the 1980's, and was used for high reliablity products like military electronics.

You probably know all this already..............

My replacement is made on a mutilayer FR4 pcb. It is deisgned to be much more electrically robust than the original "tile", which seems to suffer from voltage spikes. There are also instances of the old tiles being fragile mechanically. I know of two sharks that stopped dead in their tracks after going over a large pothole in the road !

Exactly why the old tiles fail electrically is diifcult to know. Bosch do not like to give design info away ! Some people think the failures are due to ageing of the encapsulant put over the naked chips. I think is it more to do with the semiconductor technology/process not being up to the application. There appears to be no transient suppression devices on the original tile.

My board has all manner of precautions ! Many of the devices are rated 30v.

Hope this helps !

User 4221

Thanks John!

Will you be rebuilding any L-Jets? I know this is boring old analog technology, but replacements are getting scarce.

Scott

John Speake

Hi Scott,
It's not something I've looked into. I thought the L jet ECU and also the later LH2.2 units were quite rugged and troublefree ?

It's a question of the likely demand, and where I should best put my resources.

I focussed initially on the LH 2.3 because they do seems to fail very often.

I now need some orders to fund more product development and repair services !

I remember now, we used to call the Thick film hybrid substrate "alumina"

Regards,

T_MaX

John, as soon as I get time to look for my spare LH it will be on it way to see you

Question: Is it possible for the information on the EEprom to become corrupt?

Follow-up Questions await.

Steve J.

Does everyone with a spare ecu carry it in their car? Seems like the logical place to keep it. However, when my brain failed and I pulled out the spare kept in the glove box that was tested and working a year before, it had failed, too! Which is why it took me so long to declare the brains both faulty - after all what are the chances? Diagnosed only after testing both ecu's in someone elses car. I have not had the spare repaired yet - maybe a good candidate for JDS.

John Speake

Hi T-Max,
it's pretty unlikely that the EPROM would become corrupted electronically, I would expect other chips in the ECU to also expire if the chip was overvoltaged.....

The other way to erase a chip is to take off the label to expose the window, and leave it in full sunlight for many hours (or a few minutes under a UV lamp)

But I guess a mechanical failure could happen, bond wire/lead frame/pin breakage...........

I have no direct experience of such failures yet.

Dig out that old ECU !

Regards,

John Speake

Hi Steve,
I have heard of one other ECU failing when left "on the shelf". I guess these may be more mechanical, unless struck by lightning !

Maybe that encapsulant on the chip in the tile does gradually attack the naked chips ?

I would be pleased to repair your spare unit !

regards,

Jerry 87 928S4

Question: Can you modify the ECU program? Before I had my LH controller rebuilt last year I was able to downshift to first gear at any Rpm below 6000. After the rebuild it is back to stock and will not let me downshift into first beyond 2500 RPMs. It was quite fun before. The people that rebuilt/modified my older unit no longer do rebuilds.

John Speake

Hi Jerry,
I can't modify the ECU program code yet, but I am working on this .............

However, I can't see that the LH ECU code influences the kickdown into 1st. The only input from the ECUs into the kickdown relay circuit is the tach signal, which comes from the EZK ECU.

Was your tach working OK when you could kick down at 5900rpm ? Other wise the gearbox is controlled by the kickdown switch/relay, the solenoid valve in the gearbox, and its internal hydraulics.

It might be possible to fool the kickdown relay to achieve what you want.

I believe what it does now is "normal" ? Certainly corresponds with my car.