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Thread: Ok here we go... Speedometer not working....

  1. #26
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    Timm: But Kalimer already confirmed that both fuel tank content and speed sensor pulses can be read at EKM connector X40 (brown) with a multimeter (see posts #2, #5 and #7), yet the speedometer in the cluster remains dead and also the MID does not register speed.

    We also confirmed that the three wires from the speed sensor and fuel level sensors do not have a resistive path to ground or 12V
    although I should mention that was tested with X40 disconnected. It's possible the situation is all different with X40 connected.

  2. #27
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    Yes, I saw that, but that is after moving looms to remove the connector from the EKM - I would do the same with it connected - and powered up to see if a voltage going to the fuel-level sensors - especially when wiggling stuff around.

    Also, and just as important, unless I missed it, nothing has been mentioned of the speed OUTPUT from the EKM which goes to many places including the diagnostic connector on early models - and probably close to where the fire was reported - the stuff on the speed output line is shown here:

    https://www.meeknet.co.uk/e31/e31_93.pdf#page=265

    ...it would be well worth checking that this line is not shorted to ground or 12V as it would have exactly the same effect. The reason I am veering away from EKM failure is that the car has always had varying fuel-tank level readings - and there was a small fire!
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  3. #28
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    Thanks! It looks like from the previous links you gave me, judging from the pictures, I wont have to worry about taking the dashboard out again haha

    On the other hand tho, with what I am quoting above, I only did the test with the connector disconnected. I guess I can connect it turn the car on, and just shove a probe in the plug somehow to measure???

    Ill check the connector for diagnostics as Iv yet to look at the wiring more closely in the engine bay. Another issue we had with the car is that it had mismatched DMEs, i ran the numbers and people said it was the "upgraded" or later model DME that should have worked anyway. But those DMEs were also modified with "Jet Performance" universal chips which for whatever reason made the non-original DME run really hot. Long story short we changed the DMEs out to two correct but used DMEs with stock chips. 80% of the problems went away just by getting the correct DMEs.

    The car runs fine and there really isnt any problems other than that speedometer issue.

    One thing that I did noticed is that my connectors are pretty brittle in the engine bay and some of the wiring insulation is brittle too. I broke a few connectors already, and I started to inspect and re-warp the wires with harness wire tape. I noticed that the pieces of wire that have the molded piece that fits into the connectors is expensive and it requires you to change out that piece of wire completely. I believe that molded piece is for waterproofing. I also need to find the connectors both female and male versions. Like I said everything still works but im willing to go the extra mile lol. Just on a budget.
    Last edited by shogun; 04-19-2019 at 07:36 AM. Reason: unnessary quotes removed

  4. #29
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    So im about ready to jump into diagnosing this, just so I have a plan of attack, feel free to suggest a something else, should I just go directly to all the modules and check the corresponding connector pins? I would be checking for continuity and voltage (it should be reading 0 voltage right?)

    Here is a quick plan I have:

    1.) Do all the tests I did previously but with the car powered up and note results.
    2.) Check connector pin 73 on both DME CYL 1-6 and DME CYL 7-12.
    3.) Check the remaining connectors (to the Throttle control module, auto heating/ac control module (is this the big long module thats behind the heater core housing?), servotronic, GM module and radio?) I dont have EDC so one less to check.
    4.) Trace the brown/black wire from the EKM to the speed sensor and to the fuel level sensors. I believe for that I will need to lift the car up and I might have to drop the tank. (which I need to anyway because of my fuel transfer issue between the two sides of the tank.)

    In my mind what it looks like (in simple terms) The fuel sensors and the speed sensor in the diff send out the signal and it arrives to the EKM. By doing the first test, with the car off at least everything checked out fine. So to me everything (the sensors and wiring is fine) at least to the point when it comes to the EKM. Now after the EKM I would assume the information goes to the cluster (hence the whole coding thing) and to the DMEs. Now I can tell you that I did scan the car with a OBD1 scanner that we had, but it only managed to read one DME, the DME did show that there is a speed sensor signal code.

    The odometer does not work, so my mileage is staying the same, it cant calculate the consumption on the OBC, when I press the "SPEED" button on the OBC it just shows ----- for the values. Like I said, I hope its not the EKM but the more I think of it (if I got the flow/order of things correctly) the more I think its the EKM. The weirdest part that everything worked, and then one day the dial just dropped. Hence why we thought it was the speed sensor.

    I will still go through all the testing unless someone here is going to stop me from wasting my time haha, Iv yet to test anything with either the car actually running or in the air and running.
    Last edited by shogun; 04-19-2019 at 07:36 AM. Reason: unnessary quotes removed

  5. #30
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    Scratch that last post. My gut was telling me the go and dig that EKM out and open it and really take the time to look through it. I opened it and I found this....



    [IMG][/URL][/IMG]

    [IMG][/URL][/IMG]

    [IMG][/URL][/IMG]

    Other side of the EKM (Bottom):
    [IMG][/URL][/IMG]

    You guys think replacing the resistors would be a option? I It seems like I can unscrew the brown plug from the board to check the actual condition of the board, ill do that this weekend and see.

    Basically still trying to avoid the whole coding scenario. I see used EKMs are running for 275-400 on ebay. On top of that I would have to buy a laptop running windows xp 32 bit and the other bits and pieces.

  6. #31
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    That's great progress - and it could possibly be repaired, but not easily as it looks like a couple of tracks have been burned, carbonising the PCB at the same time. The badly frizzled component is a Zener diode (marked PH-7M) - and those are fitted to protect the input/output connections.

    The pins look like 14 and 15 of X40, Speed input and Speed output respectively - so something must have shoved a few volts into one of those to damage the protection diode. So, I think the next step is to work out which pin was affected and then work out what caused it...
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


    My BMW Repair YouTube Channel
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  7. #32
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    Here is a quick timeline of everything:

    1.) Car had a small fire, the wiring which runs pretty much over the "tunnel" (under the carpet) was checked and replaced/fixed. At the same time a lot of the other wiring was checked since the interior was completely disassembled. In addition to the wiring we bought a box of all the modules from a 850 donor car (for cheap). Majority of the modules were replaced. (donor GM module had its capacitors already swapped to new ones). New batteries were also installed, along with a new transmission module and the fusible link was replaced/updated.

    2.) Took the car out for its first 10-20 min drive. Something was still up. During this drive the speedo went and the fuel gauge started to act up. Few years go by, my dad doesnt have time to play with the E31/looses interest and I buy the car from him.

    3) Found out the DMEs are mismatched and modified with the Jet Performance Chips, which are universal chips. Both DMEs got really warm/hot when the car ran for about 5 min. In addition to that the spark plug wires were bad. There was a plug or two that seemed that it was attached to the spark plug wire harness but it was not. Later I found out that the fuel pumps were on their way out (from sitting so long) I actually tested them and they went bad.

    4.) Replaced both DMEs from a donor car (matching stock DMEs) and brand new spark plugs, spark plug wires, I cleaned the distributor caps, replaced all the fuses to brand new ones and got 2 brand new fuel pumps and 2 new O2 sensors. Everything fixed itself. The last remaining thing was the speedometer and the fuel gauge problem.

    5.) Changed out the speed sensor and nothing changed. Around this time I found out that the speedo and fuel level share the same circuit and I noticed my fuel level was not reading right. The wiring around the diff sensor was checked and it was ok.

    6.) I decided to replace both baskets as I dug a bit deeper into this. I noticed that the little wires that are connected to the dials on the little level board thats inside those baskets looked burnt and really thin. The old passenger side one still worked (still replaced it as I didnt want to take any chances.) The driver side one was broken, there was no resistance reading as I moved the level. With both baskets replaced, I noticed the fuel level was reading a little bit better but it still didnt work correctly.

    7.) I basically put the car together at this point hoping to just drive the car without the speedometer until I get time to look into it. I ended up taking it out and filling it up, and I ran into a problem where I was leaking fuel. So i investigate, long story short too much fuel on one side of the tank. I believe the hose that connects both sides of the tank is bad and fuel was pushed out from that side. I ended up pumping gas from the top of the tank for prep to drop the fuel tank and inspect everything.

    8.) Meanwhile it got cold, parked the 8 in the garage for the winter and I spent time whenever I could to check the wiring again to the speedo/fuel level floats. Just FIY did not drive the car much.

    9.) My gut feeling told me to check the EKM, and I found what I found.

    10.) I realized that the EKM module could have not been replaced when modules were replaced because I would have ran into the whole "EEEE" problem on the cluster. My dad and his friend who are mostly mechanical type guys, DID NOT KNOW about this whole coding and EKM and cluster need to go together thing as well, and I do not remember anyone saying anything about the cluster having issues since the day my dad brought this junkyard rescue home. My dad actually mentioned to me a few times the cluster worked.

    Final thought: I think the EKM started to fry shortly after the fire (all the shorts and what not) but finally after the car was running (but not fully electrically sound (bad DMEs, bad spark plug wire etc)) is what it finally put it to rest. Basically during the first longer test drive. Not to mention this was in the summer too.

    So I guess now the best bet would be new EKM right? I guess I should have asked for all the things I need to code the new EKM for christmas lol. What do you guys recommend I do? Should I still take this apart and try to clean the area etc..?
    Last edited by shogun; 04-19-2019 at 07:37 AM. Reason: unnessary quotes removed

  8. #33
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    Since this is an admitted "junkyard rescue", it would seem the simple path would be to viginize the cluster and throw in a used EKM from another car.

  9. #34
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    Ouch, no wonder the speedometer does not work.

    Like Timm mentions the printed circuit board is carbonized. That is bad because carbon is conductive whereas a PCB is supposed to be an insulator. As long as the damage does not extend between solder islands of components that are hard to remove, damage like this is repairable on old school single-sided and even double-sided PCBs. The EKM PCB, however, is a 4-layer board which dramatically increases difficulty...

    It's probably a lot easier to just get a replacement EKM, although replacing the EKM with a used part does involve desoldering the shield covers and removal/programming/installation of an 8-pin IC on the PCB. So it's not exactly plug and play.

    One thing bothers me, though... In your quick timeline you mention the speedometer and fuel gauge still worked for a (short) period after the fire and repairs. This suggests the problem that caused the EKM damage may still be present... So do not install a replacement EKM until you know what happened!

  10. #35
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    Good news everyone,

    Iv had the ekm in the car for about a month now, taking it out here and there around town (car is still not done) so i was driving with the interior apart and no rear seats etc and everything works.

    I was sitting down one day and thinking about the day the speedo went out, I remembered seeing a little bit of smoke coming from under the steering wheel. At the time, my dad had the car, I didnt think of it much, I let him know but we both completely forgot about that. Long story short at that time the car had its wring fixed, all modules replaced. THE EKM WAS NOT REPLACED AT THE TIME. So when the car had its fire, Im assuming the EKM was on its last legs and when the car finally got all of its juice back it just finished that EKM off. To add to that one of the DMEs were bad which caused some electrical issues as well. The DMEs were replaced to OEM ones (the other ones were modified DMEs) everything was fine but the EKM was already dead.

    Regardless, I was freaking out that something would fry the new EKM the moment I plug it in. Maybe it would go out 3 miles from the start. I kept driving the car around since the new EKM was put it and it never showed any bad signs. After the first drive (which was like 2-3 hours driving around town, running errands) it felt the EKM and it was not hot or warm or anything. I finally put the remainder of the interior in this week. I left the rear out as I will be dropping the tank and make sure everything is good. I had separate fuel issues that were not related to the EKM.

    Its home stretch from here for my E31. Cant wait to make the film I was planning for it and share the pictures with you guys. Im sure this car will bring me more issues down the road for other things. As this is not a complete restoration. Just major restoration.

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