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C 180 W203 (97 estate) - ABS problems

Discussion in 'Suspension, Steering & Brakes' started by Phil_MK, Jul 24, 2009.

  1. Phil_MK

    Phil_MK Member

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    Had an ABS light come on (which also disabled the cruise control). Garage diagnosed as FL sensor. Changed by garage and everything was great for 2 days. Then again ABS light came on and also car went into 'limp mode' and stuck in 2nd (?) gear only.

    Took it into garage that had replaced FL Sensor and watched them go through the diagnostics. It appeared to say that now all 3 sensors were bad!!! Too much conincidence for me. Have just pumped 150 pdns already into this problems I'm reluctant to leave it with a garage who I suspect could run up an enormous bill.

    Can anyone help with the following:

    1 - Any suggestions on what it could be or things I could check? Voltages fuses, resistances etc.

    2 - I was going to try examining the overvoltage relay/fuse but I can't find them.
    I've look inside the fuse box near the driverside bonnet, removed the passenger under glove compartment but still not spotted it. Anychance someone could direct me or even send a photo?

    3 - Also, I read there maybe one under the fixed carpetted part of the floor in the boot. The haines manual shows 2 screws to remove the foor panel just behind the rear seats but mine has no screws and I can't see how to get it off. Any ideas or am I wasting my time if there's nothing there.

    Any help gratefully received. Photos of relay to Phil.Ealey@BTInternet.com
     
  2. EireJames

    EireJames Senior Member

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    Cork, Republic of Ireland
    Your Mercedes:
    Jeep Grand Cherokee OM642 power
    Hello Phil, I think you are indeed correct not to trust the garage, I have been driven mad by ABS myself over the last few weeks but all sorted now thanks to the chaps on here, mine is a 1992 E class, this thread may be of interest / help to you http://forums.mercedesclub.org.uk/showthread.php?t=51910

    I would defo check the OVP if that controls ABS on the C class you have, then I would check the resistance of the sensors (Halfords so cheap DMMs that do the job fine). Also play about with where the cables transition between engine bay and wheel arch, allow some slack in the arch to minimise any stretching on the cables as the suspension does its thing.

    If you are willing to spend some time on this you could save hundreds.

    The very best of luck and apologies that I have no C class knowledge or experience to offer.
     
  3. OP
    Phil_MK

    Phil_MK Member

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    Thanks, was an electronics engineer many years ok, so access to DMM and scopes not a problem. Just need some advice on what to look for. My frustration is that nothing appears to be where it is on other models i.e. the OV relay is not near the fuses as in 119 and from other comments, I'm not only can't find it, but not even sure it has one!
     
  4. EireJames

    EireJames Senior Member

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    Your Mercedes:
    Jeep Grand Cherokee OM642 power
    The OVP on my 250 is behind the passenger side shock, the fuses are behind the drivers side.
     
  5. EireJames

    EireJames Senior Member

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    Your Mercedes:
    Jeep Grand Cherokee OM642 power
    Quick google for "C180 ovp location" found this on another site .........

    over voltage relay protection,

    it's a big rectangular thingy under the electric ECU cover on the opposite side of the fuse box under the bonnet, easy to spot clear top with fuse in the centre..........

    Hope that helps a bit :)

    Defo check the resistance of the ABS sensors though, they should all be much of a muchness. Is the light always on or does it behave normally when the car is started and then come on when moving ?
     
  6. PhilMK

    PhilMK New Member

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    Your Mercedes:
    1999 SLK 2300, 1997 C-180 Est
    The car appears to run normally apart from 2 aspects. 1 - engaging drive is not smooth, it seems to engage a bit abruptly, 2- stuck in the same gear wont change.
    Starting to understand why I've had so much confusion, most of the information out there like http://www.detali.ru/cat/oem_mb2.as...GM=717.417&CT=F&cat=44V&SID=54&SGR=080&SGN=06 are for left hand drive cars and locations are reversed.
    I think I've located the ABS module near to the diagnostic socket behind the passenger-side strut. No sign of any OVP relay yet. I found the schematics on this site (wonderful :) ) so should now be able to trace the ABS sensors wires into the ABS ECU module and chcek the resistance as you suggested.
     
  7. EireJames

    EireJames Senior Member

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    You can test the resistance where the sensor cable is joined, it opens very easily, sort of a stubby thing about 2 inches long. Near the shocks in the engine bay probably.
     
  8. OP
    Phil_MK

    Phil_MK Member

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    Found the problem. The rear DIFF sensor is Open Circuit, the front two read 1.1K resistance each. Thank for your help, all I need to do is somehow get the sensor out!!!
     
  9. television

    television Always remembered RIP

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    I am sending you via Email the instructions that is all I have
     
  10. television

    television Always remembered RIP

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    I have sent it,,,may not be of any help,but that is all there is on this
     
  11. EireJames

    EireJames Senior Member

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    Presumablly held in my an M6 threaded hex bolt thingy maybe.
     
  12. OP
    Phil_MK

    Phil_MK Member

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  13. OP
    Phil_MK

    Phil_MK Member

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    To finish the story....

    After struggling to get out old sensor (see thread http://forums.mercedesclub.org.uk/showthread.php?t=52902 ), a new sensor was purchased for just under 60 pnds from my local Merc dealer.

    The new sensor measured 1.1K as expected. When fitted, I was a little concerned that when I turned on the ignition and started the engine the ABS light didn't go out immediately. I had to drive the card a about 20 or 30 feet before it went out and then stayed out.

    The car is no fully operational and is no longer stuck in one gear.

    I have attached a graphics detailing checking the ABS/Speed sensors to help others with this sort of problem.
     

    Attached Files:

  14. television

    television Always remembered RIP

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    So pleased that you got there :D:D
     
  15. I take it your is a w202 97, my garage said they could not read the ABS on the diagnostics for mine, pre facelift 97model so i jsut chane the brake light switch and everything has been fine so far.

    Actually i removed it, cleaned it and put it back, not changed it.
     
  16. EireJames

    EireJames Senior Member

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    Good to hear you sorted it, and no doubt saved yourself the couple of £100 the garage would have charged for replacing all of them. Well done.
     
  17. television

    television Always remembered RIP

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    Its great that we are understanding more and more about these systems,,:D:D
     
  18. Are those instructions still available? I seem to be having a very similar issue - stuck in second gear. Thanks.
     

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