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Discussion Starter · #1 · (Edited)
As many Diablo owners know, it is common to see a red error light blinking on the shock stiffness control pad on the console of the car. This is a writeup explaining what the problem is, in excruciating detail.

The Koni shock system in the Diablo is nearly the same as this system in the Maserati of the same era.

Replace all the spaces below with periods, the board software is saying I can't post links yet.

www maserati-alfieri co uk/alfieri292 htm

That page explains the system pretty well. In the Diablo, there is a Koni ECU (circuit board) in the car's center tunnel. The ECU is separate from the car's ECU. It is connected to 6 shocks in the car and the little control panel with the 4 arrows and buttons and it tells the shocks what stiffness to set to.

Inside each shock there is a little servo that turns to set the stiffness of the shock. The servo can be taken out of the shock (requires special tools). The servo is comprised of a simple little 12V DC motor, gear reduction, a rotary potentiometer on the top that uses a little brush and a small circuit board with a programmed PIC controller to read the signals from the ECU and send current to the motor.

Koni decided to control the servo DC motor from the PIC controller circuit board in the shock instead of having the ECU move the DC motors. The PIC controller itself is programmed (so you can't just replace the chip) and the actual code is likely locked down (there's a setting in PIC chips to keep it from being readable). The controller is very simple.

The DC motor itself in the servo is a 12V brushed motor. Brushed motors tend to fail over time as the brushes get worn out but I'd bet the bearings probably go on this type of motor first.

There are 3 wires going to the servo control board from the Koni ECU. They are: 12V (red), ground (black) and the control signal (blue). The 12V drives the motor.

The control signal is a PWM 5 Volt 100Hz (10ms) square wave with a duty cycle of:

5% (0.5ms pulse) for position 1 which is 0 degrees
10% (1.0ms pulse) for position 2 which is 60 degrees
15% (1.5ms pulse) for position 3 which is 120 degrees
20% (2.0ms pulse) for position 4 which is 180 degrees

The rotation may be a little under 180 degrees and I have the rotation as counter-clockwise from position 1 to 4 but I am verifying in case I messed up the polarity of the servo as I've taken it apart and reassembled it a couple times.

You can see a video of this on my website here:

Replace the spaces below with periods, I can't post links yet:

swildens com/servo html

There is a Koni shock tester that you can use with a Koni shock that has a dial that goes from 1 to 4 where you can test a shock outside of the car. You connect the shock up to it via the 3 socket plug and you can test position 1 to 4. It shows a red error light if it thinks the shock isn't working. Needless to say, not many people have these.

But you can test a servo (or shock) yourself by running a signal generator and generating the control signal yourself given the information above.

How does the Koni ECU know if the shock is working or not? When does it put up the red light?

There is no feedback mechanism. Apparently, when you start the car, the ECU sets all the shocks from position 1 to 4 and back again (or similar). When it does that, it has an OpAmp based circuit that is looking for current draw to the servos. If it moves from position 1 to 4 (and back) and sees no current draw from the motor on the 12V line as it moves positions, it will flag an error. Hopefully it also throws an error if it sees constant draw. I don't know if it does.

One issue I've seen is that if you mess up the rotary potentiometer, the motor will just spin endlessly as the PIC controller tries to find a position. So, the handling of failure on these devices isn't great. When they fail, they just do whatever they feel like.

But all they are doing is setting the stiffness of the shock so it probably doesn't matter much. Because there are 6 of these servos and the cars are getting old, lots of Diablos (and early Murcis, they had the same system) have red error lights on their Koni panel. The cars can still be driven and it doesn't mean your shock is leaking. It just means your stiffness adjustment isn't working.

The leaking shocks are another issue. There are a few people who repair those. One is John Custer who has done a lot of shocks and replaces them with different seals. Information about his work is on the board in other places.

Some people who have cars with these shocks set their ride setting to a single number, any of the numbers 1 or 4, when they start out so the car doesn't adjust the ride setting as it drives. That causes the servos to move less and theoretically would increase their lifespan.

If they do go, what are your options?

Right now, not great. The shocks aren't for sale any more, Koni apparently doesn't support them, Lamborghini doesn't have any of them. There are options for replacing the seals but not good options for fixing the servos.

I have looked at a few options myself.

First, just replace the DC motor if it is the problem. The DC motor is a common failure point. Some people have tried to get them working again by cleaning the motor but it is sealed pretty well so opening it up isn't really an option. The motor wasn't designed to be opened to get at the internals, windings, etc. I started trying to open one myself but gave up. It is probably just better to get a complete replacement.

That leads to the next problem. The size and shape. The motor is designed to fit inside the shock. And it has an integrated gears and rotary potentiometer.

I haven't mentioned it yet but my estimate on the DC motor itself is that it is about 4300 RPM or so and the gear reduction is 36 to 1. So, it is around 120 RPM (2 rotations a second) after gear reduction. That's just from counting rotations myself with a watch. Getting a perfect match isn't important because the motor is looking for its position using the potentiometer at the top. Something in the ballpark is probably fine.

It is probably easier to get a motor that has an integrated gear reduction that brings the speed down to 100rpm or so instead of trying to mate just a DC motor with the existing gearing But you still have the problem that the rotary potentiometer at the top has to fit on it right with the right screws. And the shaft on the existing one is really long to fit all that.

The company that made the motors used is supposedly out of business. I talked to some manufacturers and they want large orders to make a custom motor.

And even then, the design would be the same with a brushed DC motor, a brushed rotary potentiometer and a PIC controller on the board. The whole thing should probably be redesigned.

It is a little tricky to find a DC motor of a similar size to the existing one. The existing motor is under 16mm in diameter so a 15mm is probably the best bet. It is easy to find 16mm motors but at 15mm, the field gets narrow but they can be found.

You can buy a cheap DC brushed motor that is close to the existing one for about $7 from China (I have a few of them). Again, you'd need to get a gearhead that matched the gear reducer, that would be the main issue.

I have no perfect answer myself but wanted to put my thoughts out there on this as I look at this in case someone else is looking for information on it.
 

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Discussion Starter · #2 · (Edited)
I got a 12V brushed DC motor today from China that is 16mm in diameter. It has integrated gearing that brings the RPM down to 120RPM. It is the exact same length as the existing DC motor (including gearing) and has a longer shaft than the existing motor.

The new shaft is 3MM which is wider than the existing shaft. The existing shaft is more like 2MM.

The existing servo DC motor is closer to 15mm in diameter. The tube the servo sits in is marked 16mm inner diameter.

So, I don't know if this motor will fit. I don't have a tube to check to see if the motor does fit. It might.

The shaft would need to be machined to match the existing one. The existing shaft has a D cut, a slot and a flat end (close to 1mmx2mm end).

And the spacer from the old motor would need to be mated ot the new motor. The 2MM mounting holes on the new motor could be used to mate the two pieces if screws were found to match.

The new motor has a spur gear reduction (not planetary) so the cylinder around the gearing can be removed. The gearing assembly can be removed with a screwdriver.

If this motor did fit in the tube, then to replace the existing motor (both motor and gears are replaced):

- machine the new motor shaft to match existing one. the gearing assembly should be removed from the motor to do this so the machining can't damage the motor

- drill holes to match the motor gearing mount in the spacer and put some 2mm screws (need to find the right ones) to mate the two pieces. Alternatively, just stick the spacer from the old one on there some other way that won't get loose.

- shave down the part of the gearing on the new motor that the wires need to run down to match the old motor.

- desolder the circuit board from the old motor, then remove the top assembly (you shouldn't need to desolder the 3 wires to the potentiometer to take it apart if you desolder the circuit board first)

- reassemble everything on new motor and solder the circuit board on it

You can find the same motor I got by searching for

"16GA 120 RPM New 12V DC geared motor"

on aliexpress. It is $8 shipped and is probably the same quality as the one in the existing servo (cheap, brushed motor).
 

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I assume someone has already looked at Maserati to determine if they still have these parts? Or for that matter is there a comparable system that can be used in the Diablos as replacements?
 

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Discussion Starter · #7 · (Edited)
If I end up with something interesting, I'll let you know. I've come up with a redesign for the whole thing: motor/encoder, circuit board w/microcontrollrt, etc. But I don't have the tube the servo sits in so I can't tell if it will fit. Specifically the motor connector and wire bundle that will run out of the shock since there would be more wires. I'm talking to someone about that.

I should add that a 100Hz PWM signal does drive the existing servo but I didn't actually capture the signal from the Koni ECU myself to see if it was 100Hz. Instead, I used the information from the Maserati webpage link in the first post. I'm wondering if it is really a 50Hz PWM signal since that is more common and the 100 works because it is double 50. I'll capture it from the ECU myself with a scope at some point to verify it is actually 100Hz.

If you have a servo outside a shock and want to drive it and don't have a signal generator, you can buy a cheap PWM signal generator from Amazon for $12 (just search for PWM signal generator). Set to 100Hz, input of 5V with duty cycles above will move the servo to the 4 different positions. You also need to put on 12V to actually drive the motor. the PWM just tells the PIC controller what position to put the motor in.

I looked at the MURARA SV01A103AEA01R00 rotary sensor as a replacement for the existing rotary pot that sits on top of the motor. It is 10K Ohm, the existing one I tested at 5K Ohm so it isn't an exact replacement. That one would be small enough and the SV01 has a 1M cycle life (as opposed to the SV03). But replacing things on the existing motor is a mess because everything is custom fit.

In any case, after spending some time looking and messing with the servo, here would be my wild guess as to what would fail and the percentage chance of that being the failure point:

1. DC motor bearings 55%
2. DC motor brushes 10%
3. Potentiometer dirty/bad brushes 10%
4. Wire open - wires broken where they run outside the shock 10%
5. Circuit board goes bad 10%
6. Other 5%

So, in my opinion, replacing the motor would likely fix things most of the time. These are just my rough guesses looking at the device, of course.

Koni did sell drag racing shocks with this same system in it and they should have the same servos. I really doubt Koni had 2 different motor designs for any of their electronically controlled shocks. In a pinch, some other version of their electronically controlled shocks could be taken apart and the servos salvaged from them to repair Lamborghini servos.

The Koni shock tester I mentioned is the the Koni shock controller some drag racing cars have in them so you can set the stiffness of the shocks manually.

It is this (still can't post links, replace spaces with periods):

www yellowbullet com/forum/showthread php?t=1274202
 

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Fantastic info but this post scares me. Isn't there any other permanent and high quality /reliable solution for example, replace the shocks with new system? What about air suspension? Or what about an ABC system like Mercedes has?
 

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In the 3 years since the thread started, has there been any movement in getting a way to replace lift shock servo motors? The original post describes my situation. Usually the lift works, but the error light for adjusting the suspension is always on, and the error is no signal getting to the hydraulic part of the shock to adjust.
 

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Shark, for what it is worth my error light also blinks all the time however I can adjust the shocks, that is to say during a drive I can adjust from setting 1 to 4. It defaults to three and I rarely change it but it is still adjustable. The error light is persistent and I am not sure why even after having run the diagnostics behind the dashboard. I gave up caring in lieu of many other projects but am still curious as to a permanent fix.
 

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In the 3 years since the thread started, has there been any movement in getting a way to replace lift shock servo motors? The original post describes my situation. Usually the lift works, but the error light for adjusting the suspension is always on, and the error is no signal getting to the hydraulic part of the shock to adjust.

Bummer
My lifts out and all adjustment gone.
I looked this up optimistically hoping for a non existent solution.

Sigh.
 
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