RM European Auto Parts
Results 1 to 14 of 14

Thread: Frozen O2 sensor reading Please help

  1. #1
    Join Date
    Feb 2008
    Location
    Marietta,Ga
    Posts
    246
    My Cars
    02 e39 525

    Frozen O2 sensor reading Please help

    So i have been fighting an emissions problem for the past 2 months now when I have time.

    Parts replaced are all OEM, except for the 02 sensors Which were Bosch O.E. type.

    MAF
    Vacum Lines
    02 sensors
    Fuel Filter
    Spark Plugs (NGK iridium single prong)

    DME codes
    Bank 1 fuel trim rich
    Bank 2 fuel trim lean

    The issue that im having and cannot figure out is. According the a GT1 my bank 1 oxygen sensor is frozen at 0.4v and my bank 2 o2 sensor is functioning perfect with in parameters and fluctuating. Both sensors do work because I have switched the banks around to make sure it wasn't a fault in an o2 sensor.

    Right now it seems that all things are pointing towards a bad DME. But I just wanted to get some other opinions in what could be causing this frozen o2 sensor.

    I have also reflashed my DME with the most current software to remove that variable.


    Thanks,
    Marc

  2. #2
    Join Date
    Jun 2002
    Location
    Aberdeen, NC (yes, again)
    Posts
    23,672
    My Cars
    E39M5, E500 4WD
    Marc, it occurs to me that if you were successful in reflashing your software, your dme is likely intact. (I'm assuming you used the GT1) I would ask whether you are reading the O2 output through a scanner, or direct connection?

    "Bosch OE type" worries me, did they come with plug, or are they hand-wired?

    The spark plugs are WAY wrong, you need BGK BKR6EQUP's, and nothing else.

    I suspect a bad wire from the O2 sensor to the dme, if you're reading the O2 sensor via a scanner/ GT1, and a bad sensor heater or wiring job if you're reading direct When you say you switched O2 sensors bank to bank, and both are working, should I assume the same bank kept reading .4?

    Have you read codes? Is the car going to closed loop?

    ANYTHING to do with bad a/f ratios, I recommend a smoke test, always.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  3. #3
    Join Date
    Feb 2008
    Location
    Marietta,Ga
    Posts
    246
    My Cars
    02 e39 525
    Well the O2 sensors have the OEM connection on it. So there was no splicing involved.

    I have been using the GT1 for all diagnosing and viewing of sensors.

    and the o2 sensor in Bank one did stay constant at .4. Even when the o2 sensor was unplugged. It was reading .4 in voltage, but inactive through the controller.

    Codes that have been thrown right now are as follow.
    Rich bank 1
    Lean bank 2.

    I also did a smoke test and it showed nothing except for a small leak at the intake boot which is being replaced tomorrow if the part comes in.

    Marc

  4. #4
    Join Date
    Jun 2002
    Location
    Aberdeen, NC (yes, again)
    Posts
    23,672
    My Cars
    E39M5, E500 4WD
    Since you're using a GT1, I'll presume you also have access to factory etms and pin-outs. I'd trace the wire for O2 sensor output, verify continuity to the X6000 connector, and see if the voltage is the same through direct output of the sensor. If voltage fluctuates through direct reading, and continuity is good, computer is bad. If voltage doesn't vary when direct reading, O2 sensor is not getting hot.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  5. #5
    Join Date
    Feb 2008
    Location
    Marietta,Ga
    Posts
    246
    My Cars
    02 e39 525
    right now the car is apart. Im re doing all the lines and every little o-ring/ line I could do / may need to do soon. Just so at least that part of the puzzle is taken care of. Once all intake is put back on. im going to head over to the o2 sensors.

    Ill keep in touch and update as things develop.

  6. #6
    Join Date
    Jun 2002
    Location
    Aberdeen, NC (yes, again)
    Posts
    23,672
    My Cars
    E39M5, E500 4WD
    Please do that, answers are better than questions.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  7. #7
    Join Date
    Feb 2008
    Location
    Marietta,Ga
    Posts
    246
    My Cars
    02 e39 525
    Ok so new update,

    I know some of the stuff is irrelavent to my emissions problem. But the car does have 165,xxx miles on it so here is the entire list of repairs before I put everything back together and start daignosing.

    Valve Cover Gasket
    Water Pump
    Thermostat
    Upper Radiator Hose
    Lower Radiator Hose
    Engine Heater Hoses
    Oil filter Housing Gasket
    Intake Manifold Gasket
    Intake Boot
    Spark Plugs
    Oil Dipstick o-rings
    Secondary Air Pump Hose
    Underside Intake Manifold Hoses
    Throttle Body Gasket
    Cleaned ICV
    CCV and vacuum hoses
    Intake distribution o-rings
    Purge Valve hoses
    MAF (OEM)
    02 sensors
    Vanos Oil line
    Spark Plugs (Bosch OEM's single plat)

    All of this has been done in spare time, So did i forget anything before i get her back together or any suggestions on something that my need to be replaced or checked?

    Thanks Marc,

    P.S. just out of curiosity any one have any idea of what a quote for all this work would have been at an indy shop or dealer? I'm thinking parts included in the 4-6 thousand range.

  8. #8
    Join Date
    Jun 2002
    Location
    Aberdeen, NC (yes, again)
    Posts
    23,672
    My Cars
    E39M5, E500 4WD
    Just one quick comment: Bosch single platinums are not OEM. I highly recommend NGK BKR6EQUP's, which are the factory recommended plug for your car.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  9. #9
    Join Date
    Feb 2008
    Location
    Marietta,Ga
    Posts
    246
    My Cars
    02 e39 525
    Well I actually haven't done the sparks plugs yet i'm just gonna run my iridiums for now till I can somewhat figure out whats going on.

    As of now and after the work. it seems that all 4 o2 sensors don't have fluctuating voltages now. Which scares me since i started with just bank1 precat not fluctuating. All the precat voltages are stuck at .4 and the post cat is stuck at .5 and .6.

    any ideas?

  10. #10
    Join Date
    Jun 2002
    Location
    Aberdeen, NC (yes, again)
    Posts
    23,672
    My Cars
    E39M5, E500 4WD
    O2 heaters not functioning, sensors never got hot? May I assume that the car is reading open loop on the scanner while the sensors are reading static voltage? Does the O2 sensor voltage change at wide open throttle? How are you reading O2 voltage, through the scanner/dme, or directly?

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  11. #11
    Join Date
    Feb 2008
    Location
    Marietta,Ga
    Posts
    246
    My Cars
    02 e39 525
    at wide open throttle nothing changes. Im reading 02 Voltages through a GT1/DME. The 02 heaters i believe are functioning I just got another new set today. And it seems that they sensors are defaulting. When i unplug a post cat sensor the precat for that bank will default to .4 and the post cat will default to .7 and vice versa.

    My next move is changing Post cats which have 165,xxx on them and see if that helps.

  12. #12
    Join Date
    Jun 2002
    Location
    Aberdeen, NC (yes, again)
    Posts
    23,672
    My Cars
    E39M5, E500 4WD
    Post cat sensors have nothing to do with changing fuel mixture, they merely monitor cat's efficiency. It would seem your car's not going into closed loop - have you read "closed-loop" or "open-loop" from the GT1?

    I would consider, after checking for closed/open loop, that you try directly monitoring O2 voltage with a multimeter/scope, to see whether the primary sensors are really reading what the dme is saying they're reading.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  13. #13
    Join Date
    Apr 2005
    Location
    Connecticut
    Posts
    678
    My Cars
    95 Dakar M3, 02 Dodge Ram 1500
    I would recommend reading 02 voltages directly at the dme using a breakout box and an oscilliscope to find out if the 02 voltages at the dme are the same as what the GT1 status is reading. If they are the same I would check all wiring from the dme to the 02 sensors using either reistance or for more accuracy a voltage drop test. For a 0-1v signal little resistance in the wire can cause incorrect reading. To do a voltage drop test hook up the BOB (breakout boc) to the dme and put a pin in the signal wire at the 02 sensor. Get the vehicle upto operating temp (closed loop) and measure the voltage across the line. If you are reading fluctuating voltage of more than 0.2v than you have and issue in the wirng between the two. You may also have am issue with the heating circuit for the 02 sensor. Measure availibe voltage at the heater voltage line at the 02 sensor, i cant remember if its suppost to be 5v or 12v, but if the 02 sensor is not heating up than it will not go into closed loop and will hold voltage constant. If you have no voltage on at the heater on startup than you need to check the heater circuit. Check to make sure the relay in the fuse box is clicking over. If it is check voltage supply to relay and make sure the relay is closed circuit when clicked over (basically a normal relay test). If this is good than check resistance/voltage drop from the relay to the 02 sensor. If this is all good than you may have a DME problem. One way to see if its a heater problem is too have the GT1 connected or a voltage meater connected at this signal line in a way that allows you to drive the vehicle. Go drive it around and beat on it to raise the EGTs enough to self heat the 02 sensors. If you notice that the 02 sensor goes close loop after this than you may have a heater problem. Generally speaking though the exhaust should always be hot enough once at operating temp to keep the 02 sensor hot, thats why the heater isnt on all the time. I had an issue with this when I swapped out my OBD1 midpide for a catless OBD2 midpide. The 02 sensor on the OBD1 midpide is infront of the cat and not on the headers as yours is. When I moved the 02 sensor back to the post cat position I found that I was havin an issue with the 02 sensors if I let the car idle for 2 long. And the post cat 02 sensors should not have fluctuating voltages once at operating temp. If the voltages on those is fluctuating than you have a cat problem is well. At WOT the engine should enter open loop and fuel is sprayed based on RPM vs MAF with no consideration of 02 reading.


    It looks stock.

  14. #14
    Join Date
    Feb 2008
    Location
    Marietta,Ga
    Posts
    246
    My Cars
    02 e39 525
    Quote Originally Posted by bmwdirtracer View Post
    Post cat sensors have nothing to do with changing fuel mixture, they merely monitor cat's efficiency. It would seem your car's not going into closed loop - have you read "closed-loop" or "open-loop" from the GT1?
    I can get both OEM's for $100. So for diagnosing purposes its one less variable and another maintenance item I wont have to deal with later on. Also when you say "closed-loop"/ "open-loop" are taking in the trouble codes section after a quick test? or is there a specific function selection that I can select just like I can select in 02 voltages and o2 activity, In the function selection area?

    Quote Originally Posted by bmwdirtracer View Post
    I would consider, after checking for closed/open loop, that you try directly monitoring O2 voltage with a multimeter/scope, to see whether the primary sensors are really reading what the dme is saying they're reading.
    That is actually my plan for tomorrow or sat when Im able to get back to the shop. From what IIRC all the o2's are in connecter x60002, and start at pin 1 and then are a few empty pins till 6-11 and then i think 2 more empties and then 14-20. Or something in that area. Im actually not at the shop right now with the paper I the pins out on.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •