F355 GTS 2.7 1995 Bank 1-4 system problem | FerrariChat
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F355 GTS 2.7 1995 Bank 1-4 system problem

Discussion in '348/355' started by jlucioxim, Mar 11, 2025.

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  1. jlucioxim

    jlucioxim Rookie

    Nov 26, 2023
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    Jose Lucio Pinheiro Junior
    #1 jlucioxim, Mar 11, 2025
    Hi!

    I have a F355 GTS 1995/1995 with Bosch M2.7 system and my car began to show the following problem:
    sometimes turning the key, the check engine and slow down lights in dashboard for the bank 5-8 turned on but those lights for the 1-4 bank remained turned off. Returning the key and trying it again the 1-4 lights turned on in others attempts and I could start the car, go for a ride and return without any problem. After some days, the same thing could happen in the next use, with the dashboard lights for 1-4 bank turned off after turning the ignition key.
    I thought it could be a contact problem with the relays of the 1-4 bank. So I changed the 5-8 bank relays with the 1-4 bank relays. But the problem remained in the same way, only 1-4 lights turned off.
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    I've noticed the car had an aftermarket old alarm, so I removed it, restoring the right connections. I've cleaned the fuse box, relays and fuses too.
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    After that service, nothing changed... only the 5-8 bank lights turned on.

    So, as I'd remove the dashboard to another reason, I've checked if there was any problem with the 1-4 lights. They are ok, but turning the key only the 5-8 lights receive +12V.
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    So I decided to check if the 1-4 bank ECU had a some problem. So, I put the 1-4 ECU in the 5-8 bank and the 5-8 bank lights turned on. With the 5-8 ECU in the 1-4 bank the 1-4 lights remained off. Good news the ECU are ok!
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    At this point, my undestanding is that when I turn the ignition key, the ECU in the 5-8 bank receives power supply in the right pins but the ECU in the 1-4 bank is not receiving the same thing and is not activated. So, I looked at the F355 workshop manual repair, the electrical diagram. I had to print the 4 pages, cut them, glue them together to join the connections to notice the relays are not showed there. But by the diagram, the ECU 10, 14, 18, 19, 24, 27, 36, 37, 39 pins were import to check power supply and 3 pin could be a possible supply outpout to fuel pump relay and dashboard light.

    So, I went to check those pins. But that diagram I have it's not correct for my car. Many ECU pins stated as connected to something are not used in my F355. Here I have picture from the 1-4 ECU bank connector:
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    And from the 5-8 ECU bank connector:
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    For example: 38 and 39 ECU pins are not connected for both banks. In the electrical diaghram for 1-4 injection/ignition system I have pin 38 connected to sensor for engine revolutions and 39 connected to ground...

    Does anyone have the right electrical schematics I need?

    I checked electrical continuity from both ECU connectors to command relay 87 pin and fuel pump relay 85 and 86 pins and I haven't noticed anything strange. It seems both connectors are connected in the same pins and with similar resistance measured when compared the same pins.

    Any idea what could be the problem? Or whar are the right pins to check power supply?

    I'm thinking about to open the fuse box to check the internal links, but I don't have information about that schematics too.

    Thanks in advance,

    José Lúcio
     
  2. Qavion

    Qavion F1 World Champ
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    #2 Qavion, Mar 11, 2025
    FChat should have been your first stop... :D

    Right bank: https://www.dropbox.com/t/q8vp0SjstJKAE9vt
    Left bank: https://www.dropbox.com/t/2l2v6PjhNtJrF476
    Light circuit and car interface: https://www.dropbox.com/t/FVvDy1NP7kM7g5E4

    Give me a few moments to read through your epic post to see if you're on the right track.
     
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  3. Qavion

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    #3 Qavion, Mar 11, 2025
    Last edited: Mar 11, 2025
    The original diagrams are not very clear. My custom diagrams should show you why Motronic ECU pins 38/39 are not connected (The wiring to pin 39 is a USA modification only AND the orange wire going towards pin 38 actually bends towards pin 37).

    You seem to be on the right track, but the lamps receive power from the 1~4 injector relay. As the engine is running properly, you know the injector relay is working. There could be an issue with the wiring from the relay panel to the instrument panel.
    Also, it's the ECU which provides a ground(earth) for the lamps during start up. The ground signal goes through many connectors between the ECU and the instrument panel. There may be a connector issue.

    You may have to remove the instrument panel (partially) to access the flat white 15 pin connector on the right side of the instrument panel. This should allow you to check the wiring between the relay/ECU and the instrument panel.

    IF YOU HAVE AN AIRBAG... do not turn on the ignition key to put power on the instrument panel with the instrument panel plug disconnected. You will generate an airbag fault light which cannot be reset without a Ferrari SD1 tool.
     
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  4. Qavion

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    #4 Qavion, Mar 11, 2025
    You may not have to open the relay panel, but you may have to remove or fold it downwards it to access the backplugs. There may be other workarounds.

    Pin 87 of the 1~4 injector relay (called E5 or L) sends power (12 volts) to the instrument panel via relay panel backplug C (pin 6). The power goes to instrument panel white 15-pin plug (pin 1) via a green wire. Check the electrical continuity between the relay socket and the instrument panel plug.

    I do think it's a power issue rather than a ground issue. The ECU provides 2 separate grounds for the CHECK ENGINE and SLOW DOWN lights. It seems unlikely that both wires would have a problem (unless you have a major plug contamination issue or harness damage).
     
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  5. Qavion

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    #5 Qavion, Mar 11, 2025
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  6. Qavion

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    #6 Qavion, Mar 11, 2025
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  7. jlucioxim

    jlucioxim Rookie

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    #7 jlucioxim, Mar 12, 2025
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  8. jlucioxim

    jlucioxim Rookie

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    #8 jlucioxim, Mar 12, 2025

    What a important clue! But may car doesn't have air bag. No air bag, no alarm, no seat belts pre-tensioners, no coded key... it's a trooper!

    I only started the engine with the 1-4 bank lights turned off once. I that time the engine runned bad, only with the 4 cylinders of the left bank. So I've never tried started it again to see if the 8 cylinders would come despite of the dead 1-4 bank lights. I was running the engine only when I got to have both bank lights turned on.

    I'll test that connection between the relay and the dashboard, maybe we can solve that situation. Many thanks!
     
  9. jlucioxim

    jlucioxim Rookie

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    #9 jlucioxim, Mar 12, 2025

    Great! Thanks! I will try to verify that circuit until the next week and I hope to have good news to share!

    I removed some other parts too, as the center console, due to a leaking from a moisture removal box on the leather and it shrank. So I have little time to many things...

    Hugs,

    José Lúcio
     
  10. Qavion

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    #10 Qavion, Mar 12, 2025
    Last edited: Mar 12, 2025
    Maybe I misunderstood your original messages, José. A light circuit issue is not going to cause engine problems. Maybe it's an ECU power issue. No key power to the ECU might cause the ECU to switch off (no light and one bank operation only). Key power goes to the ECU on pin 27. This power also goes to the middle pin of the RH coilpack.

    Or it could be an intermittent relay panel internal issue. Check all the outputs of the injector relay . The injector relay also supplies power to the coil of the fuel pump relay.

    Anyway, the diagrams should help.
     
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  11. jlucioxim

    jlucioxim Rookie

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    #11 jlucioxim, Mar 12, 2025
    Looking your diagrams I have a better sight to understand the system. But taking advantage of your help, let me make two more questions:

    1- Do you know where is located that diode 30101 connected to ECU 31 pin?
    2- Doesn't the M2.7 F355 system have any knock sensor?

    Thanks,

    José Lúcio
     
  12. Qavion

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    #12 Qavion, Mar 12, 2025
    Sorry, I don't know. (EDIT) On the 5.2 car, there is a resistor hidden inside the cover of the main ECU connector. Maybe the diode is hidden there? Maybe the 2.7 car owners know?

    Strange. I thought it should have a knock sensor. I don't see one mentioned in the Workshop Manual. I don't see a knock sensor on the Ferrari 348 (2.7) car either.
     
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  13. Qavion

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    #13 Qavion, Mar 12, 2025
    Note that sometimes Ferrari wiring diagrams show diodes in their wrong polarity. If you do carry out wiring checks and get some strange results, try swapping the ohmmeter red/black leads
     
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  14. jlpjunior

    jlpjunior Rookie

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    #14 jlpjunior, Mar 15, 2025
    Hi!
    I had perfect continuity between pin 6 of connector C from the fuse relay box and pin 1 in the connector of the dashboard.
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    So, it's clear to me it's a ECU power supply problem. In the schematics you gave me there is references to figure 1, figure 2 and figure 3. What are those figures? Do you kmow where is located that 41051 rear connector RH injection system?

    Thanks in advance,

    José Lúcio
     
  15. jlpjunior

    jlpjunior Rookie

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    #15 jlpjunior, Mar 17, 2025
    Hi!
    I had perfect continuity between pin 6 of connector C from the fuse relay box and pin 1 in the connector of the dashboard.
    [​IMG]
    So, it's clear to me it's a ECU power supply problem. In the schematics you gave me there are references to figure 1, figure 2 and figure 3. What are those figures? Do you kmow where is located that 41051 rear connector RH injection system?

    Thanks in advance,

    José Lúcio
     
  16. Qavion

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    #16 Qavion, Mar 17, 2025
    Fig 1, Fig 2 and Fig 3 are written on the 3 diagrams (and in the names of the files). Fig 1 = RH bank, Fig 2 = LH bank, Fig 3 = power and instrumentation.

    41051 is in the engine bay relatively close to the ECUs. 41041 is shown here:

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    Here is the left hand side plug (I don't have a photo of the RH plug location):

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  17. Qavion

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    #17 Qavion, Mar 17, 2025
    Last edited: Mar 17, 2025
    Check for continuity between injector relay (L) pin 87 and pin 7 of connector 41051. We can't assume that the relay panel is ok. Or have you already checked pin 87 to pin 6 of relay panel plug C?

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    (mating side of connector shown)
     
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  18. jlpjunior

    jlpjunior Rookie

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    #18 jlpjunior, Mar 17, 2025
    Oh, thank you! I've seen that connector in the engine bay, but it seemed to me was a connector only for the termocouple module. And following the line from ECU connector I saw the cables on the engine inside the gap between the heads and I was praying for that connector not to be in the engine bay in the timing belts side of the engine where there are no access. :oops:
    I'm really happy to know there is a good access to that connector. :)

    Thank you very much, Ian!

    José Lúcio
     
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  19. jlucioxim

    jlucioxim Rookie

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    #19 jlucioxim, Mar 22, 2025
    Hi!

    I've found the problem with my car. As I was suspecting the problem is inside the fuse relay box. The command relay for 1-4 cylinders close contact between 30 and 87 pins but at 30 pin there is no power supply. Measuring the resistance beetween the K1 pin of fuse relay box and the 30 pin of the command relay for 1-4 bank there is no more continuity
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    While for the 5-8 bank command relay I have a good continuity between 30 pin and K1 point
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    But was good to open the engine bay connectors. There was oxidation in the right side
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    It seems the only problem with the fuse box is that disconnection of the pin 30 of command 1-4 bank relay with the power supply of 12V. Any tip of how to open that fuse relay box to avoid other damages?

    Thanks,

    José Lúcio
     
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  20. Qavion

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    #20 Qavion, Mar 22, 2025
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  21. jlucioxim

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    #21 jlucioxim, Mar 22, 2025
    There was only a screw. That I've already removed. Now there will be some clips, I can see at least four of them.
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    But it seems very fragile. Tomorrow I will try to open it.

    Thanks,

    José Lúcio
     
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  22. Timmo

    Timmo Formula Junior

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    #22 Timmo, Mar 22, 2025
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    We need you for F355 fuseboards... Enough with the factory PCB junk.
     
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  23. jlucioxim

    jlucioxim Rookie

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    #23 jlucioxim, Mar 24, 2025
    Yesterday a faced the fuse box repair rewelding pin 30 pin of bank 1-4 command relay and some others looking at them with magnifying glasses I guess welds were not too good. Now I expect no surprise fitting it again to run the engine in the next days.

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    Many thanks Ian!

    José Lúcio
     
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  24. jlucioxim

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    #24 jlucioxim, Mar 25, 2025
    Great!

    The 1-4 injection system is now working again. I could go for a ride today. Now I only have the ABS light on.

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    Thanks again!

    José Lúcio
     
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  25. Qavion

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    #25 Qavion, Mar 25, 2025
    Did you do a self test by inserting a fuse into the empty test slot (next to the luggage compartment “relay” (diodes box) with the white dot on it?

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