Hi, folks... My local Ferrari technician and I have hit a brick wall after being unable to start the engine after an engine out and engine harness replacement. His SD1 and my OBDII reader are unable to communicate with the ECU. All the wiring checks seem to be ok. Anyway, we reconnected the old engine harness to the basic power and interface plugs (without pulling the engine out again) and we got comms back! This leaves a few possibilities: A) The new engine harness is the wrong type, despite what the online catalogues tell us? P/N 170657 (Valid for USA, CND and AUS (not for F1 cars)). Maybe Daniel at Ricambi can confirm this? B) The brand new (ex-factory/OEM) engine harness is broken? C) The car may have had some dodgy wiring modifications carried out on it in the past (to perhaps stop CELs appearing)... and the old engine harness had to be modified to match the dodgy wiring? We removed a lot of the insulation from the old harness, but couldn't find any evidence of tampering (at least not relating to ECU power or OBD2 wiring). Unfortunately, no one seems to have a full wiring diagram for the 5.2 engine management system. The pre-production Bosch ECU diagram that has been floating around doesn't show how the ECU interfaces with the car power or immobiliser system. I've made several attempts at patching together a reasonable facsimile of the wiring, but keep coming across dead ends (ECU wiring disappearing into harnesses so thick, you can't track them). Would anyone know anything about the functions of the wiring going through the 3-pin OBD2 port? One pin (G) is a ground, one pin's ("L") goes to the ECU and one pin's ("K") wiring is untraceable. See plug 40210 on the diagram below. 5.2 ECU diagram (Use diagram at own risk ) The wiring harness was replaced because the wrong harness had been fitted previously (which didn't have wiring for the exhaut bypass valve thermocouple ECU), plus it had had some repairs. I've had no problems with this old harness since I bought the car over 3 years ago. However, I am fitting cats and need 3 temperature ECUs. I'm getting some useful information in private conversations, but an open message thread might be useful to others. Cheers Ian.
Thanks, John. I'll double check, but I don't think I have that 16? pin OBD port under the dash on my car. Perhaps only USA cars have these. My technician just uses the 3-pin plug near the Motronics ECU. Odd... None of those bulletin photos seem to show a grey-white wire. All these variations don't make diagnoses very easy.
OBD2: Pin 80 Brown Black, Diagnostic Port Input (OBD2) Pin 87 Red Grey, Diagnostic Port Output (OBD2) Pin 88 Brown Grey, Diagnostic Port Control Power: Pin 26 Red 12V Fused Pin 54 Green 12V Power from Relay, Pin 87B Immobolizer: Pin 56 Yellow Ignition Lock (this is the signal sent by the Immobilizer to the ECU in a pattern when you push the immobilizer button, up on receiving the correct sequence, the ECU enables ignition) Check to see if these OBD2 signals make it to the OBD2 port under the dashboard next to the steering column.
The VIN has "D" in it, Miro. I believe that's Australian delivered. Thanks, Mitch. I'll see if any of these colours/pins match my car. I hope the colours are visible and the harness isn't sealed. I didn't think of separate input and output wires. Note that the original Bosch ECU diagram says (my translation from German): Pin 80: Tacho/Board Computer [The ECU uses the crank sensor to determine engine rpm and outputs the signal to the tacho] Pin 87: Diagnostics call pin 88: Diagnostics communication I confirmed earlier that we have power on pin 26. I'll check pin 54 tomorrow. Very interesting. I wasn't sure what signal/s were being sent from the ECU. The faultfinding software said to check for continuity between pin 88 and one of the pins on the immobiliser interface unit. This was ok. I'll ask the technician if he has any tests for pin 56. The old Bosch ECU diagram shows power coming from the ignition lock to pin 88. Is it possible this wire goes via the immobiliser? I'll try to compare the old wiring with the new and see if there are any variations (in respect to all the things above). Thanks for your time, gents. Much appreciated. Cheers Ian.
Update: Fixed!!! I started comparing the old harness with the new harness and discovered that the new harness had some wires crossed. On plug 41090, pins 8 and 9 were swapped over. Some of these go to the 3-pin OBD2 diagnostic plug. Oddly, the wires were the same colours (including the stripe), so I'm guessing the factory didn't have some kind of test panel to check out the wiring properly. Prior to my wiring checks today, I think the technician must have spent at least 7 or 8 hours helping me figure out what the problem was. Perhaps I should send the bill to whomever made that new harness. Note that the harnesses being produced today may have different wire colours to the original harnesses (which doesn't help if you have a fault). In my elation, I forgot to look for that dashboard diagnostic plug and carry out some further wiring checks. Anyway, thanks for the support (moral and technical)! Hopefully the car will be ready for me to drive away tomorrow... My first major crossed off my bucket list. Hopefully the next one has a little less drama. Cheers Ian.
Fantastic news Ian I can feel your pain mate but i also feel your relief when you finally find that basted problem that gives so much grief. Well done again for your persistance.
Nice one Ian, if anyone could find the fault in the wiring it would be you! Get that baby on the road - keen to go for a drive one day too. It should be nicely sorted now.
Quick question (USA) folks.... The Workshop Manual shows only two thermocouple ECUs for the 5.2 car.... Section C39 (non-USA) and C40 (USA)..... Is the USA diagram a misprint? My Australian car supposedly has a USA-type engine management system, but I have 3 thermocouple ECUs. One for each thermocouple (2 cats plus exhaust bypass valve). Thanks.
Thanks, Tim! Not sure why the manual shows wiring going from the bypass thermocouple directly to the ECU (perhaps the manual came out before the 5.2 car was actually built... or there are 2 USA versions lurking out there)
