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  1. #1
    Active Member Two Rings
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    P0322 - CPS Overheating?

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    Car is a 2002 A4 3.0 6MT 128k miles.

    Car wont start when warm, only code is P0322 - G28 no signal.

    I replaced the crank position sensor with a new one, and still car will stall/not srart when warm.

    I can easily reproduce the problem, just let idle for 15 minutes, turn off, no re-start for a few minutes. I can confirm in VCDS measuring blocks the RPMs are at 0 while cranking when it wont start, after cooling they show up immediately and we get a start.

    One other thing is that if it does start warm, it may idle at 1200 RPMs. I unplugged the MAF during a high idle to see what it would do.. the idle bounced all around and never stabilized.

    Is it possible the new sensor acts just like the first, but doesn't seem likely.

    So the questions..

    Could the wring or a connector be affected by the heat? Is there a 2nd connector near the firewall/ecu?
    Bad ECU?
    Other issue?

    Thanks!

  2. #2
    Established Member Three Rings 5ktq's Avatar
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    That was generally a sign of a bad VR sensor, on the old audis if it wouldn't hot start, pour cold water on the crank sensor and try again... if it was the sensor dying it would start right away.

    Now a new one acting the same is pretty weird. The only connector in the path is the one you have to unplug to change the sensor, IIRC.

    Idling at 1200 sounds about right for a mostly dead sensor... that's EPC limp mode. EPC light is on I imagine? What brand sensor did you use?


    (the reason idle is high in limp mode is because the ECU quits trying to correct idle, and lets the throttle plate sit at 'failsafe' position.. which is a high idle... that why when you have a powered off TB it's open a touch.)



    Now - what is your hot start like? If it's like you have no spark at all, that is how a crank sensor failure is. If it starts but is weak and dies it could be something else.. maybe coolant sensor or something like that (bad mixture)

  3. #3
    Active Member Two Rings
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    Thanks for the input. It just cranks over like no spark.

    I got a Genuine Audi sensor today. My first replacement sensor was from a reputable dealer but sold as "OEM Brand".. and looked like the Audi logo had been removed, so not sure what is up with that. The genuine one cost more than 2x as much.

    I tapped the wires to the sensor with a DMM, but it doesn't pick up any measurable voltage when running. The erWin manual says the 2 wire sensor would be an inductor that does not get power, but produces AC. Oddly, when the car wakes up (open door/put in key), I do see 5.45v DC at the connector with the sensor unplugged. With it plugged in, don't see anything. No idea how that works, maybe some stray voltage.

    Will install this weekend, and hopefully just learned a long leason about "OEM Brand" parts.

  4. #4
    Established Member Three Rings 5ktq's Avatar
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    Yeah you'd mostly need an oscilloscope to see the signal. I don't think it has to be OEM, Bosch is good (and I imagine who supplies audi anyway)

    Though I see a lot of bosch - china stuff lately, I wonder if it is authentic from bosch plants in china, or fake, or...

  5. #5
    Active Member Two Rings
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    3rd sensor, same results.

    It must be the ECU then? I don't see any problems with the wiring.

    Swapping ECUs does not seem like an easy operation either.

  6. #6
    Established Member Three Rings 5ktq's Avatar
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    Might be a good idea to measure the resistance of the wires from ECU connector to the CPS connector, and to ground and battery (this will suck). If that's all good then that seems likely.

    I guess another problem could be the tone ring that the pick up reads could be damaged somehow but that seems pretty unlikely?


    Edit: I forgot this was warm start only problem... seems unlikely any of those faults would only exist when warm. I'm kind of at a loss.
    Last edited by 5ktq; 02-25-2018 at 08:27 PM.

  7. #7
    Active Member Two Rings
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    I think it's got to be the ECU at this point. Luckily they are cheap used, I'll have one here Friday.

    Looked at Nefmoto on how to clone the ROM and immobilizier, not as hard as I thought. You can short a pin to get them into boot mode and then copy/flash thru the OBD port with a generic cable and free software.

  8. #8
    Established Member Three Rings 5ktq's Avatar
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    Yeah I cloned mine, but the software was pretty tricky, it would take a few tries to get it to connect in boot mode.

  9. #9
    Veteran Member Four Rings walky_talky20's Avatar
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    Its not that hard to swap the ECU the correct way. Just extract the SKC from the old and new ECU's, then do the ECU swap procedure with VCDS. Personally, I'd prefer to do it that way rather than rewrite the entire ROM with software I've never used before. Much less of a nail biter. That said, clones are handy for swapping back and forth.
    ^Don't listen to this guy, he's not even a mechanic.
    2001 Laser Red A4 1.8TQM, 5-Speed Swapped, 4.11 Final Drive, APR 93, R8 coil packs, Labree HFC & DP, 2.5" Exhaust, ST Coilovers, 034 RSB, A8 Brakes Front & Rear, 18" RS4 Reps
    2006 Passion Red Volvo V50 T5 AWD 6MT
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  10. #10
    Veteran Member Four Rings Nollywood's Avatar
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    Thermal expansion issues are most likely occurring here, rather than ECU failure.

    Incorrect air gap between the CPS and tone ring could cause hot starting issues, once the aluminium expands. I take it the sensor spacing shim is fitted?

    A damaged tone ring could also cause the above symptoms.

    The CPS would not cause stalling IF it failed with a running engine. You could actually unplug the connector with the engine running, and the idle wouldn’t be affected. However, high RPM would be limited, and it would trigger the ECP light if the RPM threshold permitted with a bad sensor is exceeded.
    His:
    B6 420-TS Avant - RS6 4.2 BiTurbo, (BCY). B6/7 Hybrid "RS4" OEM Widebody Coming Soon.

    Hers:
    2002 Toyota Runx, 1.4L DOHC 16V Auto.

  11. #11
    Established Member Three Rings 5ktq's Avatar
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    I'm not sure about that nolly, ME7 runs ok without cam sensor (just has to guess what phase it is on, ok once running) - but with no crank sensor it would be completely lost...?

    Or are you thinking it fails over to running on the super low resolution cam sensor, just enough to limp with super inaccurate and conservative timing. I was pretty sure there's no such mode, G28 is pretty much the only thing it can't limp around.

    However the output of a VR signal is lowest at lowest speed (cranking), so they don't typically fail when running... if the signal is too degraded from a weak sensor it just won't start.

  12. #12
    Veteran Member Four Rings walky_talky20's Avatar
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    Quote Originally Posted by Nollywood View Post
    Thermal expansion issues are most likely occurring here, rather than ECU failure.

    Incorrect air gap between the CPS and tone ring could cause hot starting issues, once the aluminium expands. I take it the sensor spacing shim is fitted?

    A damaged tone ring could also cause the above symptoms.

    The CPS would not cause stalling IF it failed with a running engine. You could actually unplug the connector with the engine running, and the idle wouldn’t be affected. However, high RPM would be limited, and it would trigger the ECP light if the RPM threshold permitted with a bad sensor is exceeded.
    I was actually thinking this exact thing (thermal expansion/misalignment of sensor or ring) but decided against bringing it up due to lack of confidence/just-going-with-the-flow. I'm glad you did.
    ^Don't listen to this guy, he's not even a mechanic.
    2001 Laser Red A4 1.8TQM, 5-Speed Swapped, 4.11 Final Drive, APR 93, R8 coil packs, Labree HFC & DP, 2.5" Exhaust, ST Coilovers, 034 RSB, A8 Brakes Front & Rear, 18" RS4 Reps
    2006 Passion Red Volvo V50 T5 AWD 6MT
    "You need to know what you are doing...Its like a rainbow jungle in there." - Redline380

  13. #13
    Veteran Member Four Rings Nollywood's Avatar
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    Quote Originally Posted by 5ktq View Post
    I'm not sure about that nolly, ME7 runs ok without cam sensor (just has to guess what phase it is on, ok once running) - but with no crank sensor it would be completely lost...?

    Or are you thinking it fails over to running on the super low resolution cam sensor, just enough to limp with super inaccurate and conservative timing. I was pretty sure there's no such mode, G28 is pretty much the only thing it can't limp around.

    However the output of a VR signal is lowest at lowest speed (cranking), so they don't typically fail when running... if the signal is too degraded from a weak sensor it just won't start.
    You may well be correct...

    ...however, I’ve just tested this theory on my own car - unplugged the crank sensor with the engine running, and drove the car round the block. Engine remained running, though when I increased rpm and loaded the motor, the EPC light came on.
    His:
    B6 420-TS Avant - RS6 4.2 BiTurbo, (BCY). B6/7 Hybrid "RS4" OEM Widebody Coming Soon.

    Hers:
    2002 Toyota Runx, 1.4L DOHC 16V Auto.

  14. #14
    Established Member Three Rings 5ktq's Avatar
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    neat. good to know.



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