355 F1 Instrument Cluster Light for F1 Gearbox Mode

When changing the F1 Gearbox to the Auto mode the amber AUTO light in the Instrument Cluster not coming up anymore. The gearbox changes from/to Auto/Manual no problem. The light went off by itself while driving in the Auto mode.

- The bulb is OK.
- I had swapped a TCU to another one - it didn't fix the issue.
- Changing F1 relays behind the driver seat didn't fix the issue.
- I had swapped the F1 control module on the tunnel - didn't fix the issue
- I had swapped the Diodes module in the passenger footrest - didn't fix the issue.

Anybody knows of what it could be?
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Yes, I did try to swap the bulb from a confirmed working light next to. No help. I also had taken apart the whole dashboard, passenger footrest electrical board, the ECU connectors behind the passenger seat, the TCU connectors behind the driver seat, and all connectors in the tunnel I could find and clean them w/ gasoline/re-plugged all. No help. Then turned the car in to the dealers they took everything in the cabin apart and weren't able to fix it. Dealers said as soon you supply "Ground" to pin #2 that leads to the bulb, the light comes up.

I also tried to swap the ECU to another one and it also didn't fix the issue.

 

No, it does not. Other lights as you said, do.

On the Instrument Cluster, this bulb is sharing +12V with the Gearbox Malfunction Warning light (Pin #one before the last one on the LEFT white flat connector) and the Ground signal comes from the last Pin on the LEFT white flat connector. Like the dealers said when I supplied the Ground to the last pin, the light comes up. Therefore the issue is some device is not supplying the Ground when the Gearbox goes to the Auto mode.

The next step is there is no info of wrere the wire from the last pin is connected to? As there is the challenge that the F355 Workshop Manual vol. 3 having ALL the diagrams for the F355 1994/1995 where the same bulb in the instrument cluster is for CHECK ENGINE passenger side bank and this wire is connected to Motronic 2.7 passenger side ECU.

Does anybody have a wiring diagram for M5.2 F1?
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Any helpful suggestions are highly appreciated and any smart comments are not needed. Thank you.

 

No, it's not there all the time.

When I put the shortcut wire and touch the Ground having the ignition "ON", the light comes up. When I don't touch the Ground, light is not up regardless of the gearbox mode.

 

Already checked today when taking the photos, the bulb connectors on the printed circuit board are perfect. The final check was with all plugs in to the instrument cluster, I had plugged the wire to the last pin on the left white connector and was shortening it against the ignition lock surface (Ground for all cars).

Also I did check w/ the multimeter the voltage on another bulb connector which is shared with Gearbox Warning light: the Ignition key in the ON position supplies +12V to it. As I understand, when the F1 pressure drops, the TCU sends the blinking Ground to the Gearbox Warning RED light and when the Gearbox is in the AUTO mode -> constant Ground to the last Pin for the AMBER Auto light. I have a spare TCU as I mentioned swapping them didn't fix the issue so it's not the TCU. Also, there is the Pins layout in the vol. 1 of Factory Workshop Manual, there is no designated signal from TCU to the Instrument Cluster lights. If TCU sends the signal out, it's most likely modulated so it should a de-modulator somewhere in between then. And if it is, it should be a designated module for F1 as the manual gearbox cars don't need it. On the parts catalogue I don't see any devices listed.

Thank you for the tip re: turning ignition ON while connectors off the Instrument Cluster. Learned it last year actually the hard way and noted on Ferraries it DOES matter ;-)

As I understand the only next step is to learn of where this PIN is going to? Totally not possible to physically fish the wire as the wire haness is like a X-mas tree.

 

You're the man!! It's called a "Wire tracer/tracker".

Just ordered one:

LAN Tracker Wire Tracer | eBay

My only concern is the transmitter sends a signal which you go trace with a receiver but in my case there is a disconnect at the other end of the wire so the signal will not damage any equipment because of so. Definetly will switch the battery off for the trace.

 

I traced the Ground for the AUTO light coming right from an Instrument Cluster plug for the Gear Display Pin #1. Cleaning the Gear Display w/ alchogol did not fix the issue. These circuit boards don't come separately so I've ordered the unit which is the Gear Display in together with the coolant temp gauge from Italy now.
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What you referring to is rebuilding the gear display for missing pixels which they do is just changing the red LED indicator on the circuit board. It is the not the issue in here. I did have it rebuilt for missing pixels 2 years ago for $195.

 

Received the new F1 Gearbox Display with the Water Gauge (P/N for the US: 174892) from Italy which indeed does control this light and the F1 "AUTO" light is back now.
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