Could pin 4, as mentioned saying power from TCU supply relay, be another cause? I have no voltage in that pin at all. In fact is a ground line. In the manual it states that it is '+position lights'. I don't know what that means. Have any idea?
LM2903 is a National Semicondutor design opamp that is used in open feedback mode as voltage comparators. If + pin voltage is higher than - pin, the output slams to positive rail, and if the inputs are reversed, the output slams to negative rail.
Sorry, I got my wires crossed in my graphic in post #47. I described the pin functions correctly in the post previous to that, but then messed up the graphic. Here is a corrected diagram: Image Unavailable, Please Login Ferrari's '+position lights' is actually backlighting for the F1 mode selector panel provided by the display. But you shouldn't be getting earth. You should have a resistance of some sort (i.e. the value of 3 resistors in parallel with each other (but only if the voltmeter probes are the correct polarity to make the background lighting LEDs conduct). When you said I was correct about pin function, I didn't bother rechecking the graphic. I don't have any pin numbers for the panel, but backlighting power comes in on the GR (yellow/red) wire. The earth is the N (black) wire.There is a wire colour change for the yellow/red wire at the Dashboard System Connector. Image Unavailable, Please Login Since I don't have an F1, I don't know if the lights only illuminate with the exterior lights turned on or if they illuminate all the time. Do the lights only illuminate the buttons?
So... where are we up to now? Possibilities: White wire on pin 4 shorting to the data wire? Image Unavailable, Please Login Is the short damaging the serial data circuits? If you bought a new panel, would you damage it by fitting it? Or did you already disprove a wiring short by looking for continuity between pin 12 and pin 4 on the Dashboard System plug (with both this plug and the display plug disconnected?). Is it possible to inspect the entire harness going from the Dashboard System plug to the display? Are we sure that 10 volts is an error? The dc voltmeter might be reacting with the serial data chips. Would putting an oscilloscope on the data line be a better indication of what voltages are on that line?
Sorry for the late reply. Got busy in the morning and then ferrari chat was down for sometime for me.
I will ha Sorry I had not checked pin 4 properly. At that time I was solely focused on pin 5,6,7,8. That was wrong on my side. Also I will have to check the resistances as you have mentioned and also if it illuminates with the parking lamps.
I was fiddling around with my old display unit. I decided to power it on my bench with a separate battery by supplying 12v to pin 2 and ground to pin 3. Was just trying to trace where pin 5 is going to and also if I could see where the voltage to it starts from. Just using a multimeter with pin probes and being careful not to short anything. Did not get far in that. Also I found out another weird little thing, when I connect a ground line to pin 5 and disconnect it the display shows N for a second and then disappears again and becomes the 2 dashes or lines.
Serial data can be bidirectional. I don't know if it's ok to short pin 5 to ground. i.e. short the output of a transmitter. I suppose a tech guru would be able to read the data coming from and going to pin 5. We know @Wolfgang72 can do this: https://www.ferrarichat.com/forum/posts/147079085/ Anyway, 10 volts dc on a serial line doesn't sound correct.
This is no problem and quite a common scheme. For example the diagnostic K-line and L-line are working that way, bidirectional or not. The line is pulled-up by a resistor to 12V (or whatever volatge you want) and every transmitter is grounding the line, or not, to transmit serial data.
Thanks, Eric. Note that TCU is reporting that there is a short to Vcc on the dataline (i.e. a fault). There is actually a constant 10 volts dc on the line coming from the direction of the display (not from the TCU). I'm assuming this is not normal, but I'm not 100% sure. There is either a short to Vcc on the data wire or the display is generating a constant 10 volts.
I made the same measurement on a display I have. Seems OK to me. The line is pulled-up in the display. Image Unavailable, Please Login
So back to square one. We have to figure out why the TCU is reporting this as a fault. Maybe it is expecting an intelligent response from the display, not a constant voltage? Of course, we may be looking in the wrong direction. If the 10 volts is normal, maybe the TCU is just sending the wrong information in the first place (and the display is not responding). @tgaspl17 When you use the SD to change gear, does the correct selected gear appear on the display?
No it doesn't the correct gear while doing that. Maybe the TCU is reporting the error because it's not grounding it in pulses to generate the proper signals and hence it's throwing an error stating its just constantly short to vcc. Maybe it works kinda like Morse code with the dots and dashes but in this case the dots and dashes are how long it's grounding the line to the get the right pulses
Yeah even I didn't know whether it would be safe to do that or not so that's why I used the old display and not in the cars circuit.
If there is no short between the wires going to pins 4 and 12, I've run out of cheap ideas/solutions. It sounds like either your display or your TCU are causing issues. Why the TCU would report a short to battery if it (the TCU) was faulty, I don't know. Check on both sides of the Dashboard System Connector with the TCU and display disconnected.
I'll have to check between 4 and 12. Apart from that I think we have checked everything else. All that's left is the TCU. Any idea how or if we can get it repaired? I don't know know where to even start looking inside the TCU. It's a labyrinth of ferrari engineering in there. Technically marelli
I don’t understand as far as I know there is only 1 F1 warning light and yes It flashes about 4 to 15 times as the system pressurizes. Once pressurized if it finds no faults it did-lays the gear or neutral.
He meant to ask what all F1 related lamps come on with ignition. Also for some reason Ferrari has named them as ' Low friction warning light' , Automatic gearbox warning light' and 'Gearbox failure warning light'.
In my case it doesn't flash at all because the short to VBAT error is always present. Due to pin 5 of the display unit. Also when I check my pressure through SD1 it stays at 50~60bar. I get about 3 gear shifts through SD1 before the pump turns on again
Just to review With everything connected you turn your key on and the red fault light starts to flash and after so many flashes it stays on permanently and the display goes to dashes. Is this correct? I’m sorry for this but we kind of have to start at the beginning for me because of all the things you have done. I assume you have checked the f1 fuses below the passengers footrest?
Yes they warn the driver you have selected another mode, either low friction or automatic and when selected these stay lit up.
