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129, location of rear abs connectors.

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by Wearsafoxhat, Nov 3, 2018.

  1. Wearsafoxhat

    Wearsafoxhat Senior Member

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    Your Mercedes:
    05 E55k Est, 99 SL500, A200
    Having had a great summer with the car it is now refusing to be put into hibernation.
    The BAS/ESP and ABS lights have come on, the third brake light has gone out, the crankshaft pulley spat the majority of the rubber insert out and the headlamp wash/ began playing up and emptying my wash bottle.

    Being out of work at the moment thought I would see what I could rectify, keep me out from under the hoover and away from any, "could you just do, go"

    Have resolved all except the abs, bas/esp fault.
    I realise it needs to get some codes read but in one last ditch attempt would like to locate these connectors.

    Have replaced the brake light switch, suspect that the old one was okay, ( one open cct and one closed cct) have cleaned all four ABS sensors and have metered out the front ones (1k6 ohm each).

    Any pointers appreciated. Thanks


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  2. mattkh

    mattkh Senior Member

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    W168 1999 1.6
    Once the light goes out, how quickly does it come back on. Any special circumstances when it comes on ?
     
  3. OP
    Wearsafoxhat

    Wearsafoxhat Senior Member

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    Both lights came on at the same time and have remained on. They went out only once but came back on as I drove off and have stayed on since. Battery voltage is 12.5v, have disconnected the battery for thirty mins.
    Cruise control works, car runs well but sometimes does seem to hang in the lower gears a bit longer than usual.



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  4. LostKiwi

    LostKiwi Senior Member

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    Can you not just follow the wiring back to the connector?
     
  5. Hustler

    Hustler Senior Member

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    Your Mercedes:
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    If it's like the W203 then the rear ABS sensors' connection point is on the base of the rear trunk. You'll need to remove the underfloor material and possibly a large plastic casing which houses the YAW rate sensor and cables. You should see the connection point there. Again, I'm not sure how it is on the 129 but possibly something similar.

    Best option to save time is to follow the cable from the wheels to the connector as LostKiwi suggested. Takes less than 5 mins to jack the car up, get a torch light and follow the cable. :)
     
  6. OP
    Wearsafoxhat

    Wearsafoxhat Senior Member

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    I have followed the cables from the wheels to a point where they appear to enter the car in front of the diff.
    Have stripped out the boot and thought I'd ask before taking out the back seats.
    I had the car on axle stands but couldn't get to where I thought I needed to be.
    Battery 12.6 and 14.2 volts when running. All fuses good. 1998 car and 129068 vin if that helps. 38 pin obd.
    Thank you for help.


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  7. mattkh

    mattkh Senior Member

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    Just had a thought.
    Could it be the speed sensor inside the automatic gearbox ?
     
  8. LostKiwi

    LostKiwi Senior Member

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    Different symptoms. That causes problems with gear selection, limp mode, poor shifts etc etc.. Nothing to do with ABS/ESP etc.
     
  9. LostKiwi

    LostKiwi Senior Member

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    What condition is the reluctor ring in. These can get crudded up and send a poor signal to the ECU. In some cases they can split and just spin on the CV.
    Remove the ABS sensor from the hub and shine a torch down the hole. Waggle the reluctor ring with a screwdriver. If it moves it's fubared. Clean the rings with WD-40, a rag and a screwdriver.
     
  10. mattkh

    mattkh Senior Member

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    Thanks.
    I was wondering if this was relevant.
     
  11. LostKiwi

    LostKiwi Senior Member

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    The 5 speed 722.6 as fitted to this car will have adaptive shift patterns and if accelerated briskly will hold that gear a little longer in case it's still needed (quick sprints between corners for example).
    It will also hold a lower gear longer when cold to allow the catalytic converters to warm up faster.
     
  12. OP
    Wearsafoxhat

    Wearsafoxhat Senior Member

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    Thank you for the replies.
    I have removed all four sensors and all the reluctor rings are fixed and don't look too bad. Have just had a run upto London and back (160 miles) car drives as good as it usually does, cruise and speed limiter work. The bas/esp and abs lights stayed on all the way there and back.
    Am going to get the codes read this week so shall report back with the answers.
    Thank you for taking an interest in my problems with it.
    I just like the car and for the past few years have contemplated selling it but once I drive it, it becomes a keeper for another summer.
     
  13. LostKiwi

    LostKiwi Senior Member

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    If you can get the live data read from the sensors. Difficult with a 38 pin socket but if the tester can get the speed readings from all 4 sensors it will show not only which one is failing but also the nature of the failure (no signal Vs poor signal Vs patently wrong signal).

    E.g if driving at 20 and one wheel shows zero = no signal (most likely bad sensor or wiring)
    If speed shown fluctuates that's poor signal (and often corroded reluctor or split reluctor or sensor gap too high)
    If speed shown is 100 mph then that's patently wrong (bad sensor or controller).
     
    Last edited: Nov 6, 2018
  14. OP
    Wearsafoxhat

    Wearsafoxhat Senior Member

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    LK, thank you.
    Am tempted to clean the reluctor rings regardless.
    The 38 pin is the only stumbling block with the car, a few months to early for the obd2 socket, protocol. Am going to get it on star and take it from there. The more I research this problem the more complex the system is.


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  15. LostKiwi

    LostKiwi Senior Member

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    The system is actually relatively simple. A set of wheel sensors feed speed data to a controller. Using this information the controller provides information to other systems which in conjunction with other sensors perform corrective actions, the effect of which is fed back to determine what additional actions need to be performed.
    For example if braking and one or more (but not all) wheel sensors show zero wheel rotation then ABS operates to remove braking effort to those wheels. Once correct rotation is detected ABS is disabled for that wheel again.
    ESP is similar. Speed sensors detect the relative sppers of each wheel. This is used in conjunction with accelator position, yaw sensors and brake pedal operation to determine if power needs to be reduced or brakes applied to a given wheel to control its relative speed.
    If the controller on initialisation cannot get a valid reading from all sensors it disables itself and turns on the warning lights.
    From a parts perspective there are only a few - 4x wheel sensors, yaw sensor, ABS controller, brake switch, ABS pump, ESP controller, throttle pedal* and throttle body*.
    The * items are usually under control of the engine ECU which communicates with ABS and ESP. Many items are common to other systems. For example cruise uses signals from ABS (from memory left front) as does does the instrument cluster, gearbox ECU and radio (for speed sensitive volume control). Clearly the throttle system is used by the engine ECU. By looking at what has failed and what still works it's often relatively easy to determine which section has failed.
     
  16. OP
    Wearsafoxhat

    Wearsafoxhat Senior Member

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    A very nice write up. That does make it seem relatively simple, got a bit misled perhaps with yaw, tracking and steering wheel sensors on top of the other bits and pieces.
    By deduction it should be a rear abs sensor as esp is not able to be selected, info from the rear wheels required for this I pressume. However booked into to have the codes read and will post the results once sorted.
    Need to invest in a bigger jack and taller axle stands.


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  17. OP
    Wearsafoxhat

    Wearsafoxhat Senior Member

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    Just to conclude this thread.
    I found the rear connectors under the car, just needed to raise it higher to get under. They where okay to, 1k8 ohms aswell.
    The fault was with the steering angle sensor, the one in the steering wheel.
    Now all sorted, just passed its MOT with two small advisories. Now time to get it ready for hibernation, wash, wax, WD40 and battery conditioner till May.

    Thank you for the pointers



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  18. LostKiwi

    LostKiwi Senior Member

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    Well done.
    The steering angle sensor will definitely cause issues with ESP as the car won't be able to correlate the information from the Yaw sensor to what the car should be doing.
    Generally a failed wheel sensor will cause cruise to fail, but a steering angle sensor or yaw sensor won't.
     
  19. OP
    Wearsafoxhat

    Wearsafoxhat Senior Member

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    Happy that it is sorted. Have learned lots and enjoyed most of it. Shall be sorting a few things out over winter, then will face my annual dilemma, do I sell it or keep it.

    A nice drive normally makes my mind up, as does the prospect of a nice summer.


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  20. LostKiwi

    LostKiwi Senior Member

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    I know what you mean about the dilemma... But like you a drive out in it soon dispels any thoughts of selling :)
     
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