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  1. #1
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    Question MDK and Lambda problems E39 530i

    Hello guys (and girls),

    I have a problem with my E39 530i (02/2002).
    My knowledge concerning DME control is pretty good, I was trained by an Audi instructor and they use very similar hard/software, still I'm stuck and my teacher from back then is on holiday so I hope you can help me.

    My first problem has to do with the O2 sensors (pre-cat) and the Lambda-integrator. It is a euro-spec German built car with Euro 3 emissions coded in the DME. I had two cats just behind the exhaust manifold (original) and when I got the car the previous owner tempered with the O2 sensors for LPI VSI injection. As a result the sensor wires were touching the ex-manifold. I tried to save them but it didn't work, the 4 wires were melted together for all 4 sensors. The exhaust was rusted so I made a new one in SS with Magnaflow cat (400 cel). I just finished that 2 weeks ago and since I still need to install the new brake system I didn't drive the car yet. Also I just connected the pre-cat sensors, not the post cats. I was doing a bit of INPA today since I'm still waiting for my new hard brake lines and the O2 sensor voltage read 0.42 volts (not changing) and sensor heating is at 1.17%. Since the post cat sensors (not connected) have the same voltage and percentage reading I'm pretty sure that these are simulated values. Now I am considering the following reasons for this: the technical documentation for MS43 says that Lambda control (open to closed loop) only happens when the DME receives a signal from all 4 sensors, however I would think that it would still display the right voltage in INPA? Or the sensors are broken ( they are new so.... don't think so) or the voltage is not related to the milliamps it produced to give the oxygen value? I included some pictures and maybe one of you has had the same problem and found the solution?

    Second thing is that the potentiometers in the electronic throttle valve don't seem to change when engine is started and revved. The pedal position (also two potentiometers) change when I press the gas pedal and the DME calculates a correct pedal angle. But the throttle valve angle doesn't change... the potentiometers keep their values no matter how much I press the accel.pedal. Normally I would be pretty sure the potentio's in the throttle body are fried but when I turn the engine off and the butterfly valve returns to default position the signal DOES change, the potentiometers read out another value and the throttle angle goes from 0 (running) to 6 (engine off), so I assume the resistors still work? I find it annoying to ask this to you, I rather work thing out on my own but I'm getting frustrated over that car because of the amount of things gone wrong with it since I owned it. Thanks in advance! If you have any questions about this or you want to ask something about your own car I can help you with, don't hesitate!
    ps: It seems i'm having problems uploading my pics, is there a size limit? I can upload them but after that there is a "!" sign behind the and I can't drag them..

  2. #2
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    Probably best to move this to the M54 section.

    Regarding pics, yes, there is a size limit. Hover on the exclamation to see what the error is.
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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Probably best to move this to the M54 section.

    Regarding pics, yes, there is a size limit. Hover on the exclamation to see what the error is.
    Oki, will do tnx

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    let's ask @THATDONFC on this one
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    Check the fuse for the O2 heater circuit. Most likely, it popped when the wires shorted together.

    For the tps, turn the key on and check the signal voltage coming out of the throttle body. See if it reacts when you open the throttle. I believe there are 2 signal outputs. One 0-5v and one 5-0v. I can tell you which wire tomorrow when I am near my wiring diagrams.

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    Click here to enlarge Originally Posted by THATDONFC Click here to enlarge
    Check the fuse for the O2 heater circuit. Most likely, it popped when the wires shorted together.

    For the tps, turn the key on and check the signal voltage coming out of the throttle body. See if it reacts when you open the throttle. I believe there are 2 signal outputs. One 0-5v and one 5-0v. I can tell you which wire tomorrow when I am near my wiring diagrams.
    Oh man, I didn't even think about the fuses. I checked the ones in the glove box but forgot about the rest. Where is the O2 heater fuse located at? I know about the TPS potentio's and I can read their values in INPA. 2 Signals for safety idd, one at 5V fully open en 0,5V fully closed and one at 0,5V fully open and 5V fully closed. I get a signal from them but they calculate a valve angle of 0 at idle, 6 at engine off and only go op from about 3400rpm to 16 max opening... Tnx!

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    I believe the fuse is underneathe the passenger side cabin filter in the engine bay. There should be more than one fuse with it so I couldn't tell you which fuse without looking at a diagram. But most likely, you have one that popped.

    I still think it would be a good idea to measure the signal output voltage from the tps. Just hook up a voltmeter to the signal wires one at a time and open and close the throttle to see if the tps are functioning correctly.

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    Ok. The fuse is on the right hand side of the engine bay (passenger side) under the cabin filter. It's fuse #4 .

    The TPS signals should be pin 1 and 4 of the Electronic throttle plug.

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    Click here to enlarge Originally Posted by THATDONFC Click here to enlarge
    Ok. The fuse is on the right hand side of the engine bay (passenger side) under the cabin filter. It's fuse #4 .

    The TPS signals should be pin 1 and 4 of the Electronic throttle plug.
    I spent some time doing troubleshooting today and follow your advice, I got some good results from it. I connected the multimeter to throttle valve ground and to brown/purple (potentio 1) and it gave me a correct number as you can see here.

    Click here to enlarge
    Click here to enlarge


    INPA confirmed this:

    Click here to enlarge

    I continued on the second potentiometer which is brown/blue and it gave me a reading of regular battery power +12V :

    Click here to enlargeClick here to enlarge

    However INPA shows a virtual voltage of 4.19V

    Click here to enlarge

    My guess is that it is doing so to insure engine operation. I expected this to throw a fault code tho...

    I ordered a new throttle valve and it should be here Wednesday at last.

    You were right about the fuse for O2 signal/heating, I found the culprit in the electrical box under cabin filter as you said. It is tucked away in a black fuseholder that has 5 fuses in it, you have to pull the fuseholder out and open the lid it has on top. The number #4 fuse was blown (30 amps):

    Click here to enlarge

    I will let you guys know if the throttle body issue is solved.
    Thanks for your help and hope this post also helps other people out.

    Greets
    Attached Images Attached Images  

  10. #10
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    Glad I could help. Let us know what happens with your tps issue.

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    Too bad Chris, replaced TB but no luck Click here to enlarge

  12. #12
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    Next thing I would check for is a short between the output from the tps and a 12v source.

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    I was kinda thinking the same thing Click here to enlarge However I blocked that tought because I don't want to replace a loom :p I'll check it today and keep you posted! Do you happen to know how long the vacuum system should hold vacuum after engine shut off? I'm testing it after the check valve at the brake booster. I lose vacuum after about 20 seconds and I don't think that's normal! (brakes are not performing as they should...) Thanks!

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    @THATDONFC I'm getting depressed man I'm really out of ideas! The two throttle body's give the same resistance and voltages, say they are OK. I tested the 6 wires for breaks, resistance, etc etc, nothing wrong there I think 0.0 ohms, and no shorts as far as I can measure, my voltcraft multimeter is not a great one but it should do the job...

    I took the connector apart DME side so I could measure the cables directly... when I plug the connector in the DME and not in the TB and I measure voltage between + and - for actuator motor and it's 0.00V (even when I press the gas pedal) Between + en - for potentiometer (should be 5V) and it gives me nothing... .

    After, I took the cables out of the DME and connected to TB and measured the following: between Potiometer earth en potentiometer output the resistance is as it should be, it varies when I open the TB by hand, both signal 1 and 2 is good. Resistance between actuator + and - is also normal.

    When connecting the DME with the TB with engine off in ignition in II and I measure voltage over actuator it's still 0.0V (it briefly changes when I turn the ignition on and the valve butterfly clicks) but when I press acc.pedal still 0.00V, also potentiometer voltage does not change and butterfly doesn't move.

    When I start the engine the multimeter goes out of range for voltage over the actuator. However the TB responds pretty good to gas pedal... the potentiometer voltages stay the same indicating a 1 butterfly opening. Only when I press the pedal to the metal the potentiometers respond and indicate an opening of 6, however physically the butterfly is at WOT.

    If anyone has the same problem or knows the solution to it, i'm glad to hear it.
    Meanwhile I'm going to check fuses...

    Thanks

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