ferrari f355 suspension warning light

A few ideas, but they don't completely match the symptoms:

1) On some 355's, if you turn on the ignition but don't move the car, after about 3 times, the suspension light comes on. The fault will reset if you start driving the car.

2) Intermittent actuators may be the issue. I've had numerous problems with these. One one occasion, I had my local Ferrari independent plug his SD tool into the system and it identified a specific faulty actuator. I've replaced or repaired a few of mine. I now have a spare actuator for faultfinding, but the Ferrari SD tool is the quickest way to find the problem.

However, if you are not close to a Ferrari technician, make sure that the little cogs on top of the shock struts are not cracked and make sure the actuator internals are not falling to pieces. The rear actuators are fairly easy to get to. The front ones, however, are a little harder to access and you will need to remove the front luggage compartment liner to get to them. Make sure the actuators are seated properly. They may look ok, but are not fully down (and locked in place with the spring clip).

Captain Z CNC in the USA does an excellent job of repairing faulty actuators. Their website has a few tips on diagnosis.

http://captainzcnc.com/

 

One of the most useless warning lights on a 355...

 

To truly diagnose the problem, you will need a SD Tool. This is to help align the motor correctly once it is taken off the strut. Typically the gear (which the motor rotates) breaks and the computer no longer see a spike in volt/amps (which is when the gear stop is engaged aka the gear stops moving in one direction).

The gear part is relatively inexpensive and can be challenging to install (due to roll pin).

When you do pull the motor off, you can also engage the sport switch and watch the actuator rotate in one direction and then another. This can also help diagnose if the motor is bad.

Motors are not cheap brand new and can be hard to acquire.

The suspension light will also turn on, as stated above, if the wheel sensor do not see any input from the front wheels compared to the rear wheels. Typically can happen after the vehicle has been raised and started where only the rear wheel rotate.

 

This doesn't sound right to me. The wheel sensors have no input into the F355 Suspension ECU. The ABS ECU which processes the wheel speed sensor information does not talk to the Suspension ECU on this car.

If you are rotating the rear wheels, then perhaps you are triggering the vehicle speed sensor on the gearbox. The Suspension ECU can only get a sense of vehicle movement via the accelerometers behind the front bumper or via vehicle speed data from the gearbox. No comparison can be made between the front and rear wheels.

 

It's easier if you know the right technique. It involves aligning the gear part and drive shaft of the strut with a sewing needle and slipping the (hollow) roll pin over the needle.

For European customers, I guess Hill Engineering is probably the closest supplier of gear parts:

https://www.hillengineering.co.uk/suspension-steering/actuator-gears

 

You are correct. I was mixing up my logic. The suspensions light is tied to the speed sensor on gearbox.

https://www.the355.com/showworkshoppage.php?page=107&volume=2