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Thread: How To Test Cam Position Sensor?

  1. #1
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    How To Test Cam Position Sensor?

    Wondering if anybody can tell me how to test the cam position sensor (intake) and what ohms it should read at? I've had a CEL for it before. Moved car to garage and now it won't start. I tested the crankshaft position sensor which ohmed at 556 between pins one and two (which is correct I think). But I'm not getting any readings between any of the pins on the cam position sensor. Any help would be appreciated.

    Car is a 98 318ti

  2. #2
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    Ok then. Will a cam sensor with no resistance between the pins keep the car from starting? Anybody?

  3. #3
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    Got a new cam sensor, tested at about 1800, put it in, still no start. Crankshaft sensor ohms out fine, 556. Have spark, plugs are always wet after cranking, and compression is good. Why the fock won't this thing start?

  4. #4
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    I also want to see if my cam position sensor is bad. I tried to test mine by using a digital volt meter that has a fast response scale (Fluke 75). I tested between each of the 3 connection points and didn't see anything.

    Anyone have experience checking their cam position sensor?

    The reason I wanted to test this is because I did not see any type of signal at the fuel injector connection points. Fuel pump seems fine, fuel pump relay and main engine relay are also good. It will run using starter fluid, so ignition is good.

    Steve

  5. #5
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    I received a new cam position sensor, and it doesn't do anything different that my old one when I try to test it with the multimeter.

    As far as I can tell, the Cam Position Sensor can't be bench tested. If anyone has a test I'll try it.

    On my car I found a bad Crank Position Sensor by testing. Not sure how it fired up for a few seconds using starter fluid without a signal from the CPS!

    Steve

  6. #6
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    camshaft position sensor should be 12.5 ohms approx between terminals 1 & 2.

    0.4 ohms approx between terminal 2 & 3. And the car should run with a bad cam sensor
    The church is close, but the road is icy, The pub is far, but i will walk carefully

  7. #7
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    My car ran with a bad cam sensor. It was reluctant to start, required about twice as much cranking time (bad for starter) as it normally did. CEL was illuminated when sensor failed. Car would sometimes stall whilst slowing down at a stop light when driving.

    Those were mine symptoms.

    PS, I'm sure there is a way to bench test them...after all it's just a pulse generator. Perhaps a sliding magnet on sensing surface could produce a pulse ???

    Good Luck

  8. #8
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    mine did the same thing to me to i would be as slowing down and then my engine would die on me in traffic not good but everything went ok when mine starts up and i run it it sounds little bit of a miss going on not sure though i have to replace the senor soon!!!

  9. #9
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    Quote Originally Posted by Tefal View Post
    camshaft position sensor should be 12.5 ohms approx between terminals 1 & 2.

    0.4 ohms approx between terminal 2 & 3. And the car should run with a bad cam sensor
    I don't get anything near that with the new or old sensor.

    Using a magnet to create a field didn't produce any readable voltage either.

    Steve

  10. #10
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    my 635 starts well but stalls about 10 mins into a journey and then wont start again for about 15-20 mins then starts again and continues on the journey with no problems? it does not do this every time i go out in it , could this be the same problem? any ideas?

  11. #11
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    Quote Originally Posted by benny635 View Post
    my 635 starts well but stalls about 10 mins into a journey and then wont start again for about 15-20 mins then starts again and continues on the journey with no problems? it does not do this every time i go out in it , could this be the same problem? any ideas?
    Sounds more like a coolant temp sensor to me.

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  12. #12
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    thankyou that could be it, iv only just repaired the head gasket, not sure why/how the coolant sensor can stall the engine?

  13. #13
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    Quote Originally Posted by Tefal View Post
    camshaft position sensor should be 12.5 ohms approx between terminals 1 & 2.

    0.4 ohms approx between terminal 2 & 3. And the car should run with a bad cam sensor

    This could explain why ODB-II says the cam sensor in the car I am working on is dead

    I am getting zero signal from any pins, and that might also explain all of the issues this car has where it feels like the timing is off. Well off to get a new sensor and we shall see if it fixes the issue

  14. #14
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    These are strange animals. IIRC in OBD-II cars they are actually hall effect switches (sort of like a transistor) but in OBD-I they are a pickup coil.

    FWIW I had a bad CPS and it still read the proper resistance, so it must have been intermittent. All I did was remove and re-install it and that killed it.

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  15. #15
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    Right now I am trying to fix a friends 97' 318i, they did the HG and got it all back together but it runs rough as can be at idle. I finally got around to pulling the intake for them as they left it on the car and wow, the injectors and manifold had a thick layer of carbon on both, cleaning that up along with the injectors (as they looked like the carbon was blocking the spray) and double checking everything and resealing it all on the intake side fixed 5 of their 8 Error codes. All that is left is a Cam sensor and then AMM and 02, the bad 02 could be from the CPS causing the issue so I am hoping for the best.

    Either way off idle the car seems to bog like the timing is off and in lower revs it is a wee bit rough again like a timing issue. once you get over 4000 it seems to smooth out but still has a few glitches. Idle is crap and sounds like it is almost down a cyl but all cyl check out compression wise, new plugs and wires all working fine so I have a feeling if the CPS was bad the ign box might be getting a goofy signal and pulling out a ton of timing which is making it run so rough along with bog on starts.

  16. #16
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    Quote Originally Posted by Revenelson View Post
    I don't get anything near that with the new or old sensor.

    Using a magnet to create a field didn't produce any readable voltage either.

    Steve
    What kind of multimeter are you using? Hope its not a harbor freight special

  17. #17
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    How do you get to the connector for this thing? It's buried way under the intake manifold?
    DSC00560.jpg
    (Sorry for the cell-phone pic)

  18. #18
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    Feel for it baby.

  19. #19
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    I have a 99 328 and had a CEL, bad gas mileage and long turnover time. Took it to the shop and they said the CEL and bad mileage was from a bad CPS and the long turnover was because the key i had was going bad and to use a spare if i had it.

    The spare started the car with ease, but dunno if it had anything to do with the newly installed CPS.

    I guess try a spare to see if it turns over quicker?

  20. #20
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    Quote Originally Posted by boink View Post
    I have a 99 328 and had a CEL, bad gas mileage and long turnover time. Took it to the shop and they said the CEL and bad mileage was from a bad CPS and the long turnover was because the key i had was going bad and to use a spare if i had it.

    The spare started the car with ease, but dunno if it had anything to do with the newly installed CPS.

    I guess try a spare to see if it turns over quicker?
    Long turnover because of a worn key? Sounds like some BS to me.. either it starts the car or it doesn't.

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  21. #21
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    Quote Originally Posted by sweetjumper32 View Post
    Got a new cam sensor, tested at about 1800, put it in, still no start. Crankshaft sensor ohms out fine, 556. Have spark, plugs are always wet after cranking, and compression is good. Why the fock won't this thing start?
    Reply: try checking your fuel pressure regulator.It is located at the end of your fuel rail.That may responsible for your plugs soaking.

  22. #22
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    When it comes to sensors, the easiest way to see if they are dead is to get the error codes checked. I was having the 'Automatic Gearbox' warning light coming up, causing it to change into safe mode. After spending hundreds on an auto service and a few other tricks, got the codes scanned and Camshaft sensor popped up despite none of the classic signs (like non-start)

    $50, half an hour and fixed

  23. #23
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    Quote Originally Posted by benny635 View Post
    my 635 starts well but stalls about 10 mins into a journey and then wont start again for about 15-20 mins then starts again and continues on the journey with no problems? it does not do this every time i go out in it , could this be the same problem? any ideas?
    benny635, did you ever fix this problem? I'm having the exact same problem with my 2000 323i.

  24. #24
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    It is an old thread but i found a good vid that may help others
    [ame]http://www.youtube.com/watch?v=jUZAiHpuF0s[/ame]

  25. #25
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    It helped me, thanks

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