I do not know for sure but likely When the dashes are there anything could be possible because of the fault.
If the car starts normally once started if you hold the brake and select the auto mode the car should select gear 1 and should show on the display if everything else other than your paddles are working. If this is not the case you have other issues as well This will help narrow down a few things maybe
No Start the car in neutral Once running put foot on brake While holding brake select auto by pushing the button and letting the button go the light should come on on dash to (ndicate auto mode is engaged While you are still holding the brake , the transmission should select 1 within a few seconds If you release the brake and push on gas it’s will move forward if the 1 is displayed there is no way to select reverse just so you know as it’s a safety feature to get you home if the paddles quit.
Okay so small update. I tried to do the the thing taz mentioned. Start the car and hold down auto with all doors closed. But no response from the car. There's a connector below the centre console where the reverse switch assembly is. The wires run from there and go behind the fuse box and then run up and behind the dashboard. I disconnected the connector and with the ignition on and TCU disconnected there is still a voltage in pin 4 of that connector(pin 25 of TCU) but the voltage is on the side of the harness that goes to the instrument cluster. Also there is no voltage if I disconnect the gear display indicator. What is happening according to me might be that a wire that gains continuity with pin5(of the gear display connector) with ignition on is the one that has the stray voltage. Or could it be another faulty gear display even though it's new?
Also with the gear display connector disconnected there is voltage in pins 2,6,7,8. I know that 2 is the 12v pin. 6,7,8 are the friction, auto and failure warning light control. Should there be 12v in those?
In the manual it states that the warning light switching on request is sent to the TCU from the display unit. So maybe the pins 6,7,8 are the ones that are actually being short to+ve and they are jumping the voltage to pin 5(pin25 of TCU). Going to remove the pins from the display unit connector one at a time and see if the voltage from pin 5 disappears.
I was under the impression that the instrument cluster provided the 12 volts for the lamps and the F1 system provided earths (for individual fault light illumination). I don't understand why the display would be telling the TCU which lights to illuminate. Thanks for the photos! What a strange place for a dashboard connection plug. The WSM graphics and parts manuals don't show that plug at all. Removing pins from plugs seems a bit drastic. With the TCU and display disconnected, do you get continuity between pin 4 and any of the other pins on the Dashboard System Connector?
The first picture is the picture of the display unit connector. There are no pin numbers on neither the display unit or connector. Pin1 starts from bottom right in the picture and continues to the left.
Yeah removing the pins is a little drastic but I don't have a lot of options. No there is not continuity between any pins with both TCU and display disconnected. With just the display connected I get continuity between pin 5 and 12v on many places. Even checked to a couple of fuses and got continuity there as well.
For future reference, am I reading these pin numbers correctly? ... Image Unavailable, Please Login Image Unavailable, Please Login "B" is colour code white, so I'm assuming the top closest wire is on pin 1.
Ah.. I see. There is a different number of pins in each row. 1~8 (8 pins) 9~18 (10 pins) Image Unavailable, Please Login There's a gap in the 8 pin row.
When I turn the ignition on I get 9-10 volts on pin5 of the display unit connector. Also I made a mistake previously where I said I get continuity on various 12v supplies with pin5. I get 9-10v on it but it doesn't show continuity with the 12v supply. Removing pins 6,7,8 made no difference to pin 5. Also in the manual it shows that pin10 is reverse input but I don't have any wire going into pin 10. Only 9 pins.
Pin 10 of what? Which manual? There seems to be insufficient wires going from the TCU to the F1 display to cover all the functions in the instrument panel (warning lamps, gear selection, etc). At least one of those wires must be a databus line. I think that is the wire on display pin5. The display also seems to be supplying LED backlighting power (12 volts?) to the centre console selector panel. i.e. from pin 4 of the display to the yellow/red (GR) wire on the panel. I just noticed an error in my diagram (I added a junction inside the selector panel where there shouldn't be one). Updated diagram here: https://www.dropbox.com/t/ClJz8rt0jPgFLkjE I'm starting to think that the display is faulty (if there is no short to power on the pin 5 wire)
Image Unavailable, Please Login I wonder if the dataline is two-way? The display should be able to tell the TCU that it is faulty. Or the TCU may simply assume the display is faulty if it gets no response.... or the display sends an erroneous voltage signal (as described by the fault code)
Pin 10 of the display connector is empty. According to the 355 manual it should be the reverse input. I just saw your updated wiring diagram and what I noticed when I was checking voltages is that pins 6,7,8 are the various warning lamps and they all get 12v with ignition on and the connector disconnected from the display unit. I'm quite sure that's wrong because the display unit is what turns on the warning lamps. Also according to the manual the pin 5 of the display connector, which is called 'serial line', is used to send the signal to the display unit from the TCU to display gear and also to give the signal to illuminate the warning lamp that it has to. My display unit is a new one. I paid 1200£ for it. I did another thing where I removed all the pins from the display connector except 2,3 and 5. 2 is 12v, 3 is ground. I still get the same 10v in pin 5 which I'm not supposed to.
Also yes your wiring diagram is perfect. It's exactly how you've mentioned it. I just don't know why pins 6,7,8 have 12v with just ignition and disconnected from the display unit.
