Tutorial for “monitoring” the Weber Marelli IAW ECUs
(as found in the Lancia Delta Integrale)
The grale-ECU (GECU) tools are provided free of charge but without warranty or support. Here I describe how I use them.
Diagnostic Cable
The first thing you
need to monitor the IAW ECU is a diagnostic cable. The cable plugs into
the diagnostic port which is part of the big connector on the side of
the ECU. The ECU as you should know by now is inside the car in the
middle, under the dash behind the ash tray area. It is most easily
accessed from the passenger foot well. In that area you can find a
short cable with a 3 pin connector approximately the size of your
thumb. You can see this connector with cover on in figure 1.
Figure 1
The cover needs to be removed to access the signal leads. The connector without cover is shown in figure 2.
Figure 2
I
haven't found anywhere to buy the mating connector nor have I found one
the same size anywhere else in the car that could be used so I just
stuff individual pins into the connector for the time being.
The leads are as follows:
| Lead | Function |
| blue/white | ECU input |
| black | Ground |
| white/red | ECU output |
Level Converter Circuit
The
ECU uses +12v and GND for signal levels. The PC supports an RS-232
serial port which uses -12v and +12v. This means that a converter
circuit is required between the PC and ECU as follows:
| ECU side | PC side |
| +12v | -12v |
| 0v | +12v |
The ECU transmit, or output signal, is an open collector signal so needs to be pulled-up. I use a 1K ohm resistor.
Before
I knew how everything worked I built a complicated circuit with MAX232
level converters, opamps and a voltage regulator. After discussing the
interfacing requirements with Will Hoult he came up with, built and
tested the following much simpler circuit.
