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Thread: Error Code: 74

  1. #1
    QLD Administrator AdReNaLiN's Avatar
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    Error Code: 74

    Hi guys, heres my problem:

    DTC: 74
    Driving the car with the parking brake ON. ON 5 minutes
    after detection

    I can drive for 5mins with the 4ws light off and as soon as it detects the 74 error the light comes on. I am not driving with the parking brake on.

    I have pulled the 4ws computer plugs and found the green/red wire which goes to the park brake switch and tested it with a multimeter. It is functioning properly.

    The park brake wire is grounded when the park brake lever is in UP position, and the circuit is broken when the brake lever is DOWN.

    I then pulled out the pin on the plug for green/red effectively making the 4ws computer think that the park brake is never on. (why does the 4ws system care if you're driving with the park brake on anyway?)

    I then took it for a test drive, and same result, after 5mins of driving I got error 74.

    I am assuming something is wrong inside the 4ws computer?
    I did the "4ws solder dry joints" fix about 2 years ago and have had no troubles with 4ws until now.

    Any thoughts?

    This is the 4ws plug and what you need to do to pull it apart.


  2. #2
    JDM fanatic !JonZap!'s Avatar
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    do a wobble test on the handbrake, the handbrake or the wire could be damaged
    Imitation is the best form of flattery

  3. #3
    Senior Member Scotty's Avatar
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    Quote Originally Posted by AdReNaLiN View Post
    The park brake wire is grounded when the park brake lever is in UP position, and the circuit is broken when the brake lever is DOWN.

    Did you check to see if there is +12v between the park brake wire and the chassis with the brake in the down position?

  4. #4
    Premium Member AMPERAGE's Avatar
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    Quote Originally Posted by AdReNaLiN
    I did the "4ws solder dry joints" fix about 2 years ago and have had no troubles with 4ws until now
    How exactly did you go about reworking the circuit board?
    AMPERAGE

  5. #5
    Gold Member hiru's Avatar
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    Quote Originally Posted by AdReNaLiN View Post
    The park brake wire is grounded when the park brake lever is in UP position, and the circuit is broken when the brake lever is DOWN.
    are you sure the circuit it broken when the brake is down? that just means it is open circuited..... are you sure its not connected to 12V when down?

  6. #6
    Senior Member Scotty's Avatar
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    Actually I just had a look at the diagram and it looks like there is two switches that are able to pull the input low.
    One is the park brake switch and the other is the "brake level" switch. (not sure what this is??)
    In any case if either of these is holding the input low, the park brake lamp will be on.



    And here's another question..Does your park brake light come on with the brake up?

  7. #7
    Silver Member PJF_Lude's Avatar
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    scotty the brake level switch is in the resevoir, it monitors how much brake fluid is in there.
    ~Ian~

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  8. #8
    QLD Administrator AdReNaLiN's Avatar
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    Quote Originally Posted by !JonZap! View Post
    do a wobble test on the handbrake, the handbrake or the wire could be damaged
    I tested the park brake wire with a multimeter including wobbling it.

    Quote Originally Posted by Scotty View Post
    Did you check to see if there is +12v between the park brake wire and the chassis with the brake in the down position?
    There should be 0v on the park brake wire until its hooked up to the 4ws ecu.

    Quote Originally Posted by AMPERAGE View Post
    How exactly did you go about reworking the circuit board?
    There's plenty of write ups on it, basically the larger components need resoldering to the circuit board because they rattle themselves loose over time. Its a common thing on 4ws 4th gen. I believe there's a write up in the sticky of this forum.

    Quote Originally Posted by hiru View Post
    are you sure the circuit it broken when the brake is down? that just means it is open circuited..... are you sure its not connected to 12V when down?
    Yes absolutely certain, read your service manual and check the diagram yourself. It is high 12v until you pull the park brake up and it will become grounded by the switch.

    Quote Originally Posted by Scotty View Post
    Actually I just had a look at the diagram and it looks like there is two switches that are able to pull the input low.
    One is the park brake switch and the other is the "brake level" switch. (not sure what this is??)
    In any case if either of these is holding the input low, the park brake lamp will be on.



    And here's another question..Does your park brake light come on with the brake up?
    It seems neither switch is holding the input low scotty.
    Yea the park brake light works perfectly.

    Quote Originally Posted by PJF_Lude View Post
    scotty the brake level switch is in the resevoir, it monitors how much brake fluid is in there.
    Correct.



    So here's the thing ^ none of those things matter when i've driven the car without that wire connected to the 4ws computer at all... I did the equivalent of cutting the wire so there is absolutely NO connection between 4ws computer and park brake.

    This means effectively the 4ws computer should be detecting that the park brake lever is DOWN at all times.

    The error 74 still occurs.
    I believe its a problem inside the 4ws computer. I will be swapping it out for a spare one I have and seeing if it makes a difference.

  9. #9
    Senior Member Scotty's Avatar
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    Quote Originally Posted by PJF_Lude View Post
    scotty the brake level switch is in the resevoir, it monitors how much brake fluid is in there.
    Thanks Ian I didn't know that

    Quote Originally Posted by AdReNaLiN View Post

    There should be 0v on the park brake wire until its hooked up to the 4ws ecu.

    Yeah I don't think so. Without looking at it I'd agree that the input to the 4ws ecu would be internally pulled high but if you look at the diagram the input is also connected to the 12v via the ignition switch and in series with the brake light bulb. If you have the input disconnected and if neither of the two switches are on then you should see 12v between the wire and ground.

    I think as a final test I'd disconnect the input again, Turn the Ignition switch to IG1, check that you have 12v on the wire (with respect to ground) and also 12v at the input of the ecu.


    Either way I'm keen to see what you find out.

  10. #10
    QLD Administrator AdReNaLiN's Avatar
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    I definately DONT have 12v on the wire (with respect to ground).

    I will check to see if there's 12v at the ECU input when I get home. I left the seat out etc so its easy to get to the plugs.

  11. #11
    Gold Member hiru's Avatar
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    Quote Originally Posted by AdReNaLiN View Post
    The park brake wire is grounded when the park brake lever is in UP position, and the circuit is broken when the brake lever is DOWN.

    I then pulled out the pin on the plug for green/red effectively making the 4ws computer think that the park brake is never on. (why does the 4ws system care if you're driving with the park brake on anyway?)
    Quote Originally Posted by hiru View Post
    are you sure the circuit it broken when the brake is down? that just means it is open circuited..... are you sure its not connected to 12V when down?
    Quote Originally Posted by AdReNaLiN View Post
    Yes absolutely certain, read your service manual and check the diagram yourself. It is high 12v until you pull the park brake up and it will become grounded by the switch.
    sorry bud i dont know much about the 4th gens but i'm just going from whats been said...

    but it sounds like what you did when pulling out the wire to effectively make it think the handbrake was down is wrong.. it sounds like you should be putting 12V to that pin to simulate the handbrake being down? you have said two contradicting things.... that is if i understood what you said correctly.

  12. #12
    Senior Member Scotty's Avatar
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    Quote Originally Posted by AdReNaLiN View Post
    I definately DONT have 12v on the wire (with respect to ground).

    I will check to see if there's 12v at the ECU input when I get home. I left the seat out etc so its easy to get to the plugs.
    Ok cool. This has been an interesting thread btw with great input.

    Here's the diagram.
    Note how the input is also indirectly connected to the 12v via the brake lamp. That's why I reckon you should see 12v on the wire (at the 4ws ecu plug) regardless of being connected to the ecu or not.

    Cheers.


  13. #13
    Senior Member Scotty's Avatar
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    Quote Originally Posted by hiru View Post
    sorry bud i dont know much about the 4th gens but i'm just going from whats been said...

    but it sounds like what you did when pulling out the wire to effectively make it think the handbrake was down is wrong.. it sounds like you should be putting 12V to that pin to simulate the handbrake being down? you have said two contradicting things.... that is if i understood what you said correctly.
    I think Steve is assuming that the input to the ecu is internally pulled high. So if you disconnect the wire the input will sit at 12v.
    It's common practice to do inputs like this but I'm not sure if it's been done that way in the 4ws ecu. I'm going to check mine tonight just out of interest.

  14. #14
    QLD Administrator AdReNaLiN's Avatar
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    I havent contradicted myself... here's a diagram of my understanding.

    batt. +12v_____________________________________________+ 12v 4ws computer
    ````````````````|
    batt. 0v ______brake lever switch

    I think Steve is assuming that the input to the ecu is internally pulled high. So if you disconnect the wire the input will sit at 12v.
    It's common practice to do inputs like this but I'm not sure if it's been done that way in the 4ws ecu. I'm going to check mine tonight just out of interest.
    Yes, I was of that assumption as per my diagram above.

  15. #15
    Gold Member hiru's Avatar
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    Quote Originally Posted by Scotty View Post
    I think Steve is assuming that the input to the ecu is internally pulled high. So if you disconnect the wire the input will sit at 12v.
    It's common practice to do inputs like this but I'm not sure if it's been done that way in the 4ws ecu. I'm going to check mine tonight just out of interest.
    ahh rito... now i'm on the same page ahaha....

    not sure about the input being set at 12V if the wire is disconnected though. normally pins are set to default ground if anything... (not sure specifically in relation to the ecu's though). if the multimeter doesnt show up with 12v it might be worth testing it by putting 12V to it. however you may need a pull down resistor to ground to make this work....

    are you sure the inputs are 12V? seems high for what is pretty much a mircroprocessor system. i would have thouht they would have used ttl levels... perhaps there is a converter inside?

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