Desoldered from the ECU: the hybride circuit Prototype1 Prototype of 928-diag-tool running on PC
About "928-ECU-repair"
The owner of 928-ECU-repair with a big smile in his 928 S4
The car:
The madness on the 928 starts for me when I was kid....During holidays
watching fancy Porsches on the German motorways... What a beautiful car...
Since a few years I'm able to buy such a Porsche, but finding the correct one,
is very difficult. But after 2 years searching I found in the summer of 2004
a black metallic 928 S4 from the '90. The car had driven only 104.000 KM
which is not much. Oh, the first testdrives where and are still fantastic.
But the counterpart of the car is the maintenance. Repair when something is broken
otherwise..One of the modules inside the car, which fails most of the time after
more than 10 years is the Electronic Control Unit (ECU or Bosch LH Jetronic).
The one in my is still the original but I know that time will get me.... So I decided
to start in december '04 a new project: repair the ECU. A friend of mine had already
replaced his ECU from a 928 so he had the broken one left in his garage. It was no problem
to borrow it. In the meantime I gather information from the internet about LH-Jetronic systems.
I found information that most of the time that the bottleneck of the ECU is the thick film
hybride circuit.
What is the problem ? The Integrated Circuits (IC) on the thick film are made with the
internal components exposed and then the IC is filled with kit to protect the
internal components. Unfortunately the kit that they selected is shrinking and/or
expanding with changes in temperature over the years and finally cracks which
also cracks and damages the internal components of the IC in the process.
Background:
I studied information-technology at the University of Eindhoven and
currently I'm working as an embedded software architect at a typical Dutch
electronics firm. I borrewed a logic analyser from my work and start to
compare the broken ECU with the one in my car. But also I did the comparison
during a testdrive.
Very soon I discovered the problem of the broken ECU and I
repaired it with success. The problem was indeed the thick film hybride circuit mounted
on the ECU. I started to develop a replacement of the thick film hybride component.
See picture on the right side of my first prototype of the hybride. To test this prototype I drove many
hours in extreme weather conditions without any failure.
Previous job:
In the past I wrote many software for the 80C51 (is the main micro controller in
the ECU). Reading and understanding the assembly code is also
no problem. At home I have a complete 80C51 debugger with trace-facilities so
it is only a matter of time to understand the ins and outs of the ECU.
And finally in my previous work, I learned everything about car diagnostic.
Porsche 928 S4 is one of the first cars with diagnostics on board. I cannot be
difficult to understand the protocol on the L/K-lines.
So a second project was born: do your own 928-diagnostics. No expensive Hammer-tool or
other tools, no, it must be a simple connection between 928 and PC.
With some components and software running on the PC, I'm able to do my own
928 diagnostics. The diagnostic tool helped me also to improve and
finalize the replacement circuit of the thick film circuit.
First product:
A few months ago the same friend told me, why don't your start you own bussiness with
all the information and prototypes you build. Yes why not. But to make a good
product out of it, you have to do more. The circuits I selected for the
replacement are all according automotive specifications. That means for instance
that the IC operate without failures at extreme temperatures.
Further to make a good layout and Printed Circuit Board(PCB) is also not an easy job.
Again some facilities on my work helped me to develop a correct PCB.
Second product:
The second product, which is available too, is able to communicate with the modules
in the car. With commands, I'm able to activate some tests, read faultcode, clear the
fault codes, read input signals from several modules. Further it is possible to do realtime
knock count.
You can find more and detailed information about the products
I offer on the left side.
PM of 928-ECU-repair.