There's been a lot of bullshit told by Maserati about how this system works.
Oil charged with metal particles, shocks able to sense the condition of the route
and to adjust themself. Certainly many others. It's time to see how it really works.
I described internals of a QP4 adjustable here.
It's in French but pictures are sufficient to understand principles.
Note that 224/424/Ghibli/QP4 shocks are all built same way and can
be mixed in the same car.
Actually front and rear shocks can be mixed as well.
The system works only if all four shocks work.
The system contains:
The Koni shocks have slightly different length compared to standart ones but they are still inter-changable.
There are two versions of the control panel:
The pictures below show the servo-motor located in the shock.
We see a motor, gear, position pot and electronics. It's a classic servo-control
design. It's powered by a 12v supply. And it's controlled by a classic PWM pulse signal.
Computer sends a 5v pulse every 10ms. Pulses are 0.5/1/1.5/2 ms long for four positions.
One may use a standart RC model servo-controller to adjust shocks. However beware of noise
on the line that may make servo positionning not precise.
Inside the computer is like that:
We can see:
Each time there is a change of the shock adjustment the MCU expects it to consume current during some amount of time. The OpAmp senses this current and sends a binary signal to the MCU if consumption is significant. This is how MCU knows that each shock works.
All shocks get the same control signal and in the same time.
When computer is powered up it first sends two different positions to all shocks. If the observed
consumption is compliant to its expectations then it switched off the status LED and the
system is ready.
If an abnormal behavior was observed then computer makes 4 attemps to set these two positions
and then lights on the error LED.
If no control panel is connected then shocks are left in position 1 (softest).
Next picture shows the whole wiring harness
Even if MCU knows exactly which shocks have unexpected behavior it does not give us this information.
I observed two error codes:
There is way to cheat the computer to make it think all shocks are present even if
only some of them are actually connected (see wiring below).
We can use the fact that the the control signal is the same for all shocks and that all
the computer expects is a proper current consumption on each shock. If the ground wire of a not connected
channel (of a shock) is connected to a ground of another actually connected channel then
computer sees shocks on both channels. This is easy to do with a shunt on the computer's connector.
The wiring harness contains a 1-pin red connector that should be near the control panel
or the selection button. This connector is normally open.
If you close it (at any time) the system enters the diag mode in which computer cycles over the following steps:
The shock connector pin out:
I did not try to know where every shock is connected to the computer. So let's call them 1..4.
The computer 25-pin connector pin out:
Position inputs 1 and 2 receive a binary encoded number of the requested position from the control panel.
We get the four 00/01/10/11 combinations. I don't know which code is for which position.
The control panel can be replaced by two 2-position switches that close the inputs to the ground.
The four combinations will encode the four adjustment positions.
It's not surprising that after some amount of working hours the servo-motor will wear and die.
However there is another source of failures: the cable. The servo cable that links
motor to the shock connector can be worn exactly where it enters the shock.
Below is a picture of the cable wires as I found them:
