ecu reset mk4

Discussion in '1.8 & 1.8T' started by mk2 dabbsy, Mar 4, 2009.

  1. mk2 dabbsy Forum Member

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    hi i recently done a ecu reset to try and sort the problems on my car i have been told if you dissconnect the battery for 24hours the ecu will go back to stanard and set itself all back up is that right?? also does it matter wat terminals you take off as i took off the possitive one not the earth should this make a difference??
     
  2. mk2 dabbsy Forum Member

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    bump anyone??
     
  3. mk2 dabbsy Forum Member

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    Someone Must No Or Have A Idea!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!plz Help Me!!!
     
  4. nickh89GTi Forum Member

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    Try uk-mkivs.net has loads of info on there for MK4 and 5's
     
  5. nickh89GTi Forum Member

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    From what i have read its a couple of hours. Any fault codes will soon come back when you drive the car though. Its not a fix :lol:
     
  6. marty1979 New Member

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    To do an ECU reset on my Skoda RS, which has the same 20v lump in as the mk4 golfs just a bigger turbo, you disconnect the battery for a couple of hours, re-connect, then switch ignition to position 2, the throttle body should squeal for about 10 seconds. After the throttle body shuts up, switch off the ignition, then fire up the motor but don't touch the accelerator at all for 10 min's. After 10 min's take for a spirited drive as the ECU is an adaptive unit and needs to learn new things e.t.c. Hope that helps
     
  7. mk2 dabbsy Forum Member

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    ok thankyou do i have to dissconnect the possitive or the negative or will it not make a difference??? also wat is possition 2?? how longshall i leave it dissconnected for?
     
  8. marty1979 New Member

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    Disconnect the negative terminal for about 2 hours, it may be worth switching your lights on while the battery's off too, just to make sure that the ECU is totally drained of power. Position 2 is the second click on the ignition, just before the starter motor fires up. Don't forget to let the engine idle for 10 min's before you touch the throttle when you start it after the reset, then go out and have a nice fun drive.
     
    Last edited: Mar 11, 2009
  9. mk2 dabbsy Forum Member

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    ok cheers buddy will it matter weather i disconnect the negetave or the possitive???? as i disconnected the possitive and it didnt do anyhting. please help cheers m8
     
  10. marty1979 New Member

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    It shouldn't matter which terminal is removed really, I usually take the negative off though. What are you expecting to happen when you reset the ECU? Normally a reset should be done after installing an aftermarket air filter, or have an after market exhaust fitted e.t.c. You mention earlier that you're having prob's with your car, a reset will clear codes but if there's a fault somewhere it will just flag again. What's up with your motor, I'll try and help you out if I can:thumbup:
     
  11. mk2 dabbsy Forum Member

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    ok mate well its basicaly runnin real slow recently. so i plugged it into vag.com and it said i have a faulty cold water temp sensor so i changed that and now the car runs really cold wont even go up 2 90 on the gauge!!! it did before.. any ideas i dont think the thermostat is stuck open as it was fine before i changed it i only changed it cause vag.com picked up that as a fault!!! but basicily i just think it runnin a bit slow and now its runnin really cold i have unplugged the maf sensor and took it for a drive and it makes no difference to the preformance which is strange?:thumbup: can u help?????
     
  12. Crispy 8V CGTI Committee - Club Secretary Admin

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    dis connection will only clear the 'low' memory which include the basic settings & possibly the actual light on
    fualts will still be stored

    best thing is do get it plugged in, what stored fauts are there? thermostat issue?? heaters hot? very likely to coolant temp switch
     
  13. mk2 dabbsy Forum Member

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    ok mate well its basicaly runnin real slow recently. so i plugged it into vag.com and it said i have a faulty cold water temp sensor so i changed that and now the car runs really cold wont even go up 2 90 on the gauge!!! it did before.. any ideas i dont think the thermostat is stuck open as it was fine before i changed it i only changed it cause vag.com picked up that as a fault!!! but basicily i just think it runnin a bit slow and now its runnin really cold i have unplugged the maf sensor and took it for a drive and it makes no difference to the preformance which is strange? can u help?????
     
  14. marty1979 New Member

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    If there is no change in driveability when the MAF is unplugged, then that would suggest a faulty MAF sensor. Do you have a K&N filter on the MAF? If so then the oil from it could've fouled the wire which reads air temperature. It can be cleaned but I'll run that by you later if it isn't completely dead. Usually the engine will stumble when you plug the connector back into the MAF, if nothing happens then the ECU is probably ignoring it completely and using a basic map, which is why the car feels slow. Also there is a pipe that comes off the bottom of the turbo that is known for leaking air, you'll see it if you get under the car and look up at the turbo, tell tale sign is oil running down the side of the pipe.
     
  15. mk2 dabbsy Forum Member

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    yes mate it has got a airfilter on it but its on the end of a long carbon pipe behined the front bumper. so u could be right how do i clean the maf? i have wiped it out with a rag before i dissconected the maf sensor wen the car was runnin before and it did splutter and cut out then it would restart and run ok but still slow. then wen i plugged it back in it spluttered again. how do i tell that if the maf is dead??? what will i need to do to fix it?? any ideas buddy??? u seem to no ur stuff :)
     
  16. nealey Forum Junkie

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    You cant clean a maf and if you have tried then you have moe than likely destroyed it
     
  17. jedi_stylie Forum Member

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    Disconnecting the MAF is a myth.

    Cleanig the MAF is a very short term solution. You can clean it by spraying it with electric contact cleaner. http://uk-mkivs.net/forums/p/18018/532522.aspx#532522

    Does your car have a misfire under load in 2nd and 3rd? Then id just get a recon MAF from VW, which is 70 once you hand in your old one.

    Temp sensors are a common problem too, only 25ish from VW. This could be causing the problem.

    Also, check for boost leaks http://uk-mkivs.net/forums/t/190273.aspx

    Luke
     
  18. marty1979 New Member

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    What do you mean disconnecting the MAF is a myth? It's not true that disconnecting the MAF has an affect on driving performance? I disagree. How is the ECU supposed to get a reading from a sensor that is not connected? If the sensor is non functioning for whatever reason then it will be ignored and a pre-written map will be used in it's place. This pre-written map will have no variables at all, so therfore the air/fuel ratio will be at a costant value, hense the poor performance. The only feedback the ECU has in this case is from the O2 sensor. A dodgy MAF connected can have a worse affect on driving performance than with it disconnected, "limp mode" in some cases will run better, so disconnecting the MAF can show a fault if there is one. All this is in my own experience, Skoda Octavia Vrs running 220+ bhp thanks to a jabba remap.
     
  19. badger5

    badger5 Club GTI Sponsor and Supporter Trader

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    MAF disconnect, and if the car runs stronger IS EVIDENCE that the MAF is goosed.
    not a myth, a diagnostic fact.

    why?

    when connected but under reading (dying) the ecu cannot know it is under reading ad will assume the low level of metered air is all thats passing it by.. It can and will trip mil codes for adaption limit exceed on lambda as it tried to correct a situation of MAF saying 100g/s was being drawn in, when in reality 150g/s was, so short fueling lean by some 50g/s, which lambda tries to correct but cannot when the gaps is too large.

    when disconnected ecu has to run on the other tables, which generally runs richer, so when performance seems to be better for a disconnected MAF its 99% certain the one in there is poorly.
     
  20. mk2 dabbsy Forum Member

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    i have disconnected my maf wen the car is runnin and it splutters then dies but will start again i took it for a drive and no difference. what should i do????
     

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