F355 5.2 motronic Electrical problem

I thought I'd better go back to your original message as that mentions the source of the original problem. Unfortunately, we don't know if there is melted wiring which has caused a short circuit or an open circuit. If there is an open circuit somewhere between the ignition switch and the engine, then you will have to break up the circuit into segments and check each segment.

1) to make sure the ignition switch is working correctly, disconnect the plug on the steering column and check the resistance between the red wire and the light blue wire with the key in ON/RUN

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2) The wiring diagrams show two blue wires going from the ignition to the relay panel. If there was an open circuit on one wire, then the power would simply go through the other wire. However, I know on the 348, the diagrams show two blue wires, but on some cars there is only one. Does your car have two blue wires? i.e. on the car side of the plug (not the lock side).

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Since your HVAC is not working and there is no power going to the rear of the car, then perhaps we can assume that there is no power going to the relay panel or something has melted inside the relay panel.

If there is a short to earth causing lack of power the rear of the car and to the HVAC, then we have to treat this differently. I doubt the ignition lock has a short (as that is what is required to make an ignition lock work (i.e. "continuity").
If there is a short on one of the blue wires going to the relay panel, you may have to disconnect both A & C plugs on the back of the relay panel and check for a short to ground on the blue wires.

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i.e. disconnect the ignition lock plug and check the resistance between the blue wire and ground.

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Unfortunately, we haven’t had much luck finding replacement parts for ignition locks. There were rumours that a Fiat ignition switch was suitable for 355’s, but I think they are hard to find.

Here’s a message thread relating to a 348 ignition switch. The Fiat switch was missing the Accy position though.

https://www.ferrarichat.com/forum/threads/ferrari-348-ignition-switch.585995/

In theory, you could short the ON and ACCY wiring together. I don’t think I’ve ever needed to use the ACCY position except as part of fault diagnosis. This way you won’t have to change the ignition lock and door locks. Keeping your car OEM comes at a large price and a lot of work. I’m not sure which way I’d go.

Sorry, no experience on the earlier Ferraris. This is best left to the experts on the 308/328 forums.

 

There seems to be plenty of second hand Ferrari 355 switches for sale. Perhaps you could rob parts from them and fit them to your old switch?

Just be sure to buy the correct type … USA/Canada or Rest of World.

 

Hi Qavion, would it be possible to make those links live again? Looking for the wiring diagram on for the 2.7 ecu based F355

 

These links will be more appropriate to the 2.7, assuming you want engine and brake diagrams for 1995 and later....

Teves brakes: https://www.dropbox.com/t/jGvq13Ql3ZCdPodt

Ignition: https://www.dropbox.com/t/5ygUNJM9cY1XQNY4

Engine management (right bank): https://www.dropbox.com/t/LPkpLxE0ZVg5NVoE

Engine management (left bank) : https://www.dropbox.com/t/C9prp1deZx7ODBfk

 

I'm not sure how you're getting voltage on the black/white wire. It should be connected to the main engine earth. I don't know how you'd find a short to power on this wire. It's connected to dozens of things.

On which side of connector 41051 are you getting voltage (with the connector, disconnected)?

 

Sorry to jump on this thread I’m just to find a complete set of wiring diagrams for a 2.7 355. I know @Qavion has posted some great wiring diagram’s for 5.2.
Can anyone help

 

Hi, Barry. Normally I don't hand out diagrams to people with only 1 post without knowing a little about their background and current car issues. Maybe if you fill in your profile, at least I have some idea which diagrams to send you. Although I've done my best to ensure their accuracy, they come with the usual caveats, such as "even Ferrari gets the wiring wrong sometimes". This is especially true if you are professional tech whose customers rely on you to make the right diagnosis.

Maybe start a new thread with your current issues and I can point you to the right diagrams? Also, that makes it more interesting for everyone.

 

The earth network on the non-ECU side of the plug is a real nightmare.

Here's the alarm diagram:

https://www.dropbox.com/t/3UktL0ojIuaXN5Ay

You'll find the connector in the bottom RH corner of the diagram. From pin 7, it goes to splice "30074/30083". The immobiliser siren's black wire is also attached to this splice, so you may have found your problem. I would suggest disconnecting the siren to see if the voltage goes away but it's not easy to get to. On my car, I had to remove the LH front wheel liner to get to it. A leaky internal battery may have caused a short.

Having said that, the stray voltage may be coming from somewhere else and affecting the siren.

 

I've highlighted the connection between the siren and the ECU connector in this diagram to make it easier to follow:

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There are no fuses for the Immo ECU as far as I can see. The ECU takes power directly from the battery bus bar behind the passenger footwell relay panel and from the ignition key (via wiring in the relay panel). On later cars (360, etc). they decided it was an issue and added a fuse.

 

Nope. I usually mark this on my diagrams if I know where they are (as they are so hard to find).

Sorry, I don't follow your logic. Why the ECU and not the siren? The battery supplies live power to the ECU and the siren.

Sirens are know to blow fuses on the 360 (same siren type). The siren would be my first choice, especially if the siren is buzzing.

 

According to the wiring diagrams, the siren and ECU use different terminals on the battery bus bar behind the passenger footwell relay panel. I'm not sure how you'd figure out which is which.

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Thanks to @yelcab for image.

 

I believe that disconnecting the siren makes the LED illuminate continuously (experts?), but no other ill-effects.

Do you mean the air pump or the idle air controller (IAC)? My IAC takes a few seconds before it shuts off (same as the dash lights). E13, the ignition/injection relay powers the IAC. The relay is controlled by the ECU. The secondary air pump is powered by relay E10 (also controlled by the ECU). With just the ignition on (no start), only the IAC operates.