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Thread: P1550 error

  1. #1
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    P1550 error

    Finally have my 8 running and on the road again after having the full engine and trans out of the car - feels terrific, but I'm getting a P1550 CEL (Idle Speed Control Valve Closing Solenoid Control Circuit Electrical). Any suggestions on trouble shooting before I start disassembling everything?

    1996 840Ci

  2. #2
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    First of all - make sure it is plugged in! The error is a report from the DME that it has not detected any current demand from the ICV.


    The ICV can be seen in the centre of this picture with the pipe running in from the left - the connector is on the left-hand end in the picture:
    Last edited by Timm; 04-13-2019 at 04:13 PM.
    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. #3
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    Yep - it's plugged in. I did have the whole harness off when I pulled the engine, so not 100% sure everything upstream of the plug is perfect... Does anyone know the pinouts for the three conductors on the plug that I could test the solenoid while it's off the car? (I'm pretty glad it's easy enough to get to!)

    Or maybe the fuse location? The diagram says it's a 30amp fuse somewhere, but I don't see it in the fuse box under the hood
    Last edited by Spandrel; 04-13-2019 at 04:39 PM. Reason: Additional information

  4. #4
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    No separate fuse, it is controlled via the DME - and the respective diagram is below:

    https://www.meeknet.co.uk/e31/e31_95.pdf#page=199

    Fuse finder here:

    https://www.meeknet.co.uk/e31/Timms_...use_Finder.htm
    Last edited by Timm; 04-14-2019 at 04:50 PM.
    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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  5. #5
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    Thanks! (I was going off the diagram in the E38 Bentley manual and hoping it was similar). So is it possible to test the solenoid by energizing pins 1 and 3? 12V? Or would the DME put out a different voltage? I don't want to order a new unit if instead I should be chasing wiring issues...

  6. #6
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    You can test it with a meter - set to the low Ohms range - there should be continuity between all three pins (of a few Ohms). If any pin is open circuit then the device is a dead one.
    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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  7. #7
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    OK, no open circuits on the unit- pins 1-2 and 2-3 show 12-14 ohms and 1-3 shows 26 ohms. I tried to follow the other end of the circuit using the electrical manual you linked below, but I'm not sure I'm reading it correctly. It looks like pins 1 and 3 of the unit got to pins 2 and 29 of X6000 which (I think) is one of the two 88 pin connectors in the E-box on the (US) passenger side. Not sure which one. I tried testing continuity from pins 2 and 29 of each to pins 1 or 3 of the connector, but not sure I'm doing it right. Also tried to check the intermediate connector (X6821? X6825?) Over the cylinder bank but couldn't find a listing for that 25 pin circular connector. Not sure my next steps here... Any suggestions?

    Quote Originally Posted by Timm View Post
    You can test it with a meter - set to the low Ohms range - there should be continuity between all three pins (of a few Ohms). If any pin is open circuit then the device is a dead one.

  8. #8
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    With the ignition switched on Pin 2 of X6130 (the connector that plugs into the ICV) should have 12V or so on it (RED/BLUE wire) - this is supplied from the main DME relay via a couple of splices (X6824 and X6821). The other two pins connect directly to the DME via X6000 on WHITE/GREEN and WHITE/YELLOW wires.

    In spite of this error does the engine idle at the correct speed?
    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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  9. #9
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    The engine does appear to idle correctly (just under 700RPM or so). I will occasionally have a difficult start, but not often.
    I'll check pin 2 this evening when I get a chance to pull it apart again.

  10. #10
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    With key in ignition on or with engine running: Pin 2 is at 4.87V, pin 1 is at 5.04V and pin 3 is at 0V (at the connector) It seems to idle at an appropriate speed, but my OBDII is not here right now, so I can't give you a specific RPM...


    Quote Originally Posted by Timm View Post
    With the ignition switched on Pin 2 of X6130 (the connector that plugs into the ICV) should have 12V or so on it (RED/BLUE wire) - this is supplied from the main DME relay via a couple of splices (X6824 and X6821). The other two pins connect directly to the DME via X6000 on WHITE/GREEN and WHITE/YELLOW wires.

    In spite of this error does the engine idle at the correct speed?

  11. #11
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    That seems to be the problem then, pin 2 does not have 12V on it. That 12V supply also is the source of power to the EGS and a whole lot of other modules, so it must be present up to the splice X6821. As long as you are sure you measured correctly then you need to trace the RED/BLUE wire....
    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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  12. #12
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    SOLUTION! Root cause turned out to be that I had swapped the plugs for the inlet speed air control valve and the throttle position sensor. They are immediately next to one another and the same shape - the IAC valve is GREY and the Throttle sensor is BLACK. Figured it out when I got to peeling the rubber boots back from the plug to check the wires and they were different colors than in the manual you included, Tim. Thanks so much for your help!
    (Really kind of disappointed that the BMW engineers didn't Murphy proof the design a bit better. The plugs are almost touching, and are easily swapped (especially as things get dirty and oily and BOTH plugs look black))

  13. #13
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    You wouldn't believe how many times plugs get swapped over - usually the throttle position sensor and the ASC+T throttle position sensor on the M60/M62!
    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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