ABS Light and Loss of Brake Assist | FerrariChat

ABS Light and Loss of Brake Assist

Discussion in '348/355' started by SethP, Feb 18, 2018.

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  1. SethP

    SethP Karting

    Jul 2, 2014
    83
    Corning, NY
    Full Name:
    Seth Parks
    I’ve been having an issue with my brake/abs system where it will build pressure with the key in the on position but not once the car is started. It will charge the system and recharge after pumping the pedal without the engine running. Once the car is started I don’t believe it recharges at all. I am getting code 2.1 for the abs which is Valve or connecting wire defective or defect in control unit (power transistor).

    I have bled the brakes, checked fuses and have a relay for the pump on order. Not sure what it could be given the symptoms. Any ideas?
     
  2. brendon0

    brendon0 Formula Junior

    Dec 13, 2003
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    Tampa FL
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    Brendon
    What year?
     
  3. SethP

    SethP Karting

    Jul 2, 2014
    83
    Corning, NY
    Full Name:
    Seth Parks
    Oh, sorry. It’s an early 95.
     
  4. brendon0

    brendon0 Formula Junior

    Dec 13, 2003
    611
    Tampa FL
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    Brendon
    the 95 uses a ford teves system not a bosch in the 96+

    power the car on (not start)

    listen for the pump to stop - should run
    under 2 minutes

    pump the brakes 4-5 times and count
    how many times it takes to activate the
    pump.

    you should be able to get 3-5 pedal pumps
    to get it started again
    this is usually a good sign means eveything
    is working

    report back the results

    also does both the brake and abs lights come on at he same time when you lose power brakes?
     
  5. SethP

    SethP Karting

    Jul 2, 2014
    83
    Corning, NY
    Full Name:
    Seth Parks
    Yup, did that. See first post. Works as normal with key on. Engine on or key in start position, nothing. Abs light comes on first then brake light follows soon after.
     
  6. brendon0

    brendon0 Formula Junior

    Dec 13, 2003
    611
    Tampa FL
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    Brendon
    is there power to the pump when the car is running?

    check befor cranking and after.

    maybe you have a sticky relay or something
    can you swap the relay with another same
    amp relay and check it?
     
  7. SethP

    SethP Karting

    Jul 2, 2014
    83
    Corning, NY
    Full Name:
    Seth Parks
    I have not tested for power at pump when running but I suspect there is none. If you turn the key to start and let off before it fires the pump does not run so it has to do with the key position not whether its running or not.

    I replaced the main abs relay and will be replacing the pump relay as well before digging deeper. I don’t know what else could cause these symptoms. Ignition maybe...? Any other thoughts?
     
  8. m.stojanovic

    m.stojanovic F1 Rookie
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    Dec 22, 2011
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    Power to the ABS pump relay comes through the yellow ABS relay (182 on the diagram) when this relay is OFF. The yellow relay is energised and switches ON during cranking which disconnects power to the ABS pump relay so the pump will be inactive. After the key is released from the START position, the yellow relay should go OFF to reinstate power to the ABS pump relay (and re-activate the ABS ECU). It appears that in your case the yellow relay, once energised while the key is in START, does not go off when the key is released. A few things to check:

    1. Do you have the correct (yellow) relay in this position (it has two diodes inside it so a standard 5-pin relay will not work)

    2. Check the ground point 140 on the diagram (it is probably near the ABS compartment)

    3. Start the engine and, while it is running, pull the yellow relay out and listen for a "click" at the moment of its disconnection from the socket; put it in again to when the pins just start touching the socket and again listen for the click; if the relay clicks, it means it stays energised, for some reason, while the engine is running and interrupts power to the ABS pump and a signal to the ECU.

    4. If you have the click of the yellow relay, you can do another test: with the engine still running and the yellow relay removed, using a short length of wire with spade connectors on each end, connect the short wire between positions 30 and 87a of the relay socket; this will reinstate power to the ABS pump and ECU, i.e. you will have the same condition as before cranking the engine (when your ABS works).

    Then see if your brakes work well while driving with the bypass wire in. Otherwise, the wire that energises the yellow relay to switch off the ABS during cranking comes from the key switch (its START position terminal) but it is also connected to the "Test device for warning light" (102 on the instrument cluster diagram). If your yellow relay is correct and good and the ground point 140 is good, then it is possible that his "device" is faulty causing the yellow relay to stay on. I don't know where it is located, looks like somewhere under the dashboard.
     
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  9. m.stojanovic

    m.stojanovic F1 Rookie
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  10. SethP

    SethP Karting

    Jul 2, 2014
    83
    Corning, NY
    Full Name:
    Seth Parks
    Great, thank you! I’ll investigate this tonight. That relay sounds like a likely culprit. I believe all of the abs relays are correct. Do you have a wiring diagram?
     

    Attached Files:

  11. m.stojanovic

    m.stojanovic F1 Rookie
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    Dec 22, 2011
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    Your yellow relay may not be the correct type. Can you take a picture of its schematics (it should be on the side of the housing) and post. See the cut-out from the 348 diagram below.

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  12. Qavion

    Qavion F1 World Champ
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  13. SethP

    SethP Karting

    Jul 2, 2014
    83
    Corning, NY
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    Seth Parks
    So I have done some testing and am now even more confused! It seems like the yellow relay may be sticking because with the engine running (abs pump not) I can turn key back to accessory then immediately back the run before the engine stops and the abs pump will start working. It appears that I have the correct Hella yellow relay and good ground. Upon removing the yellow relay with the engine running the starter engages! I can’t comprehend how this would be possible. After studying the wiring diagram the only thing I can think of is a faulty ignition switch or an issue with the harness.

    Any ideas? Am I missing something?
     
  14. yelcab

    yelcab F1 World Champ
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    Nov 29, 2001
    12,661
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    You have 45 posts in 4 years so we don't know you. Please give some history before jumping into troubleshooting mode. Is this your car? Is this a customer's car? Did this happen all of a sudden? Or after something or someone did something to it? Is there a possibility of miswiring or relay in the wrong socket?
     
  15. m.stojanovic

    m.stojanovic F1 Rookie
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    Do you have an additional starter relay?
     
  16. boxcarracer

    boxcarracer Formula Junior

    Jul 29, 2005
    333
    Montreal
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    Luigi
    My car exhibits the exact same symptoms if a starter relay is installed. Without it, everything works perfectly.
    Hoping to get to the bottom of it once it's out of storage.
     
  17. m.stojanovic

    m.stojanovic F1 Rookie
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    I think I have mentioned earlier, in a couple of posts, that a standard cube relay is not really suitable to be used as an additional starter relay because it can cause issues, the typical one being the starter motor continuing to run when the key is released from the "START" position. The relays that work well are as pictured examples below (motorcycle starter relays or universal small starter relays, i.e. relays that draw at least 1 Amp to engage).

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  18. SethP

    SethP Karting

    Jul 2, 2014
    83
    Corning, NY
    Full Name:
    Seth Parks
    Thanks everyone!

    Yes, it is my car. It’s been my daily for the past 8 months. She’s a 95 black on black berlinetta with 59k. It’s been a very trouble free car. Everything was working perfectly for months until the brake light came on and I lost brake assist. I did have an issue with the starter a few months ago for which I installed a relay to solve. I considered that that could be the issue but when I removed it I had the same issue. What issue does this actually cause? I’m trying to wrap my mind around what is happening.

    Does anyone have a part number for one of these relays?
     
  19. brendon0

    brendon0 Formula Junior

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    did the diode relay go bad maybe? can you test it with a multimeter?

    (not sure how to test - electrons only flow 1 way so I think can probe the circuits and switch the +/- to see if you get voltage thru it on one direction)
     
  20. m.stojanovic

    m.stojanovic F1 Rookie
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    It is easy to verify correct operation of the yellow ABS relay. Connect 12V, '+' to pin 86, '-' to pin 85, the relay should click; 12V connected the other way around, the relay should not click. Same goes for the ABS Pump black relay.

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  21. SethP

    SethP Karting

    Jul 2, 2014
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    Corning, NY
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    Seth Parks
    Yup, when tested the relays appear to be in working order.
     
  22. m.stojanovic

    m.stojanovic F1 Rookie
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    If your starter motor engages when you remove the yellow ABS relay, then you must have a starter relay somewhere. You did not mention what car you have - 355 or 348; if 355, is it F1 or manual; is it 2.7 or 5.2?
     
  23. Qavion

    Qavion F1 World Champ
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    Do you mean you installed an additional relay to the starter circuit? How is it wired in?

    Old electricians' motto: If in doubt, go to the last modification.
     
  24. SethP

    SethP Karting

    Jul 2, 2014
    83
    Corning, NY
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    Seth Parks
    Yes, I did install a starter relay a couple months back. Despite my initial tests I does now appear to be the issue. It’s a 355 2.7 gated.

    I tried installing a motorcycle starter relay as suggested but it didn’t work (need to do further test to determine why). Then I put a standard normally open relay in that I had and everything worked great for several starts then it stopped working. By stopped working I mean I’m back to my original problem where the car starts but the brake pump doesn’t work with ignition on after cranking.

    Relay wiring is as follows:
    30 to power block in engine compartment
    85 to ground
    86 to starter signal wire from ignition
    87 to starter
     
  25. m.stojanovic

    m.stojanovic F1 Rookie
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    I have made a simple diagram (extract) of the 355 2.7 Starter Motor and ABS Relay wiring (when I say "on both sides" below, I mean pins 85 & 86 of the relay)

    In the original arrangement (no additional starter relay):

    Ignition ON - Relay R is switched on by the blue wire, gets ground through the (inactive) Starter Solenoid; Yellow Relay is off as it has ground on both sides (one direct, one through the inactive Starter Solenoid) and the ABS has power.

    Ignition START - Relay R is switched off as it gets +12V on both sides (the line to the Starter Solenoid becomes positive); Yellow Relay is on as it gets +12V from the now positive line to the Starter Solenoid and power to the ABS is disconnected.

    Ignition back to ON - both relays go back to the condition as in "Ignition ON"

    With inserted Starter Relay:

    Ignition ON - Relay R is switched on by the blue wire, gets ground through the coils (which are in parallel) of the Yellow Relay and the Starter Relay (Relay R gets reduced current/voltage, as it does not have more direct ground now like through the Starter Solenoid very low resistance coil, but enough to switch it on); Yellow Relay will be off even though its coil now gets some positive current from the coil of the Relay R but, since the Yellow Relay and the Starter Relay coils are in parallel, this current is split into two branches one of which is not enough to switch the Yellow Relay on.

    Ignition START - Relay R is switched off; Yellow Relay on (no power to the ABS); Starter Relay on (engine cranks).

    Ignition back to ON - Relay R is back on; Yellow Relay stays on (no power to the ABS) - this is because every relay needs certain voltage/current to energise but, once energised, it will stay on with relatively small voltage/current; the current it gets is from the Relay R coil which flows through both, the Yellow Relay and the Starter Relay coils but the Yellow Relay is probably more sensitive than the Starter Relay (has probably weaker return spring) so it will stay on whereas the Starter Relay, probably with a stronger return spring, will switch off. When the Yellow Relay is disconnected while the engine is running, the current that flowed through its coil (from Relay R coil) is now re-directed to the Starter Relay coil which, with this additional current, is switched on and engages the Starter Motor.

    If a small starters type of relay is used for the inserted Starter Relay, universal or motorcycle starter relay (a large type of motorcycle relay, not if it is small and similar to the cube relays), the problem described above will not occur as the coil of such relay will have much smaller coil resistance than standard cube relays and will better simulate the coil of the Starter Solenoid (the path to the ground when inactive) which has been taken out of the circuit. Before inserting any of these more robust relays, make sure that they draw at least 0.5 Amps (~20 Ohm coil resistance) to engage, around 1 Amp is better (~10 Ohm coil resistance).

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