Audi A4 2.0 TDI (2008) BPW Cab - G28 Engine Speed Sensor Implausible Signal 16705/P0321/000801

Discussion in 'Audi TDI forums' started by 2012S3, Oct 7, 2015.

  1. 2012S3

    2012S3 New Member

    Joined:
    Apr 15, 2012
    Messages:
    9
    Car:
    2002 A3 Tdi (130PD)
    2008 2.0 TDI BPW A4 Cab - 80k

    16705/P0321/000801 - Engine Speed Sensor (G28): Implausible Signal
    Implausible signal G28 engine speed sensor rough running / engine cut / buck and some black smoke above 2k rpm with glow plug flashing around and above + 2k with aforementioned symptoms - settles back down fine when you lift off - some 128 faulty injector signals mentioned in measuring blocks but suspect thats the G28 causing it.

    Engine starts and idles fine. - Checked G28 engine inductive speed sensor wiring to/from ECU to sensor / checked relucter wheel for integrity - no missing teeth and running true / not loose
    - Both G28 and G40 camshaft hall sensor have been scoped and are being measured correctly. (also checked timing teeth on cam sprocket are not bent)
    - All earths in engine bay good with low resistance 002 Ohms.
    - Checked fuel pick up up
    - Clamped return hose of tandem to build pressure as didn't have the correct pump pressure tester but made no difference to symptoms.
    - Checked for signs of oil in filter.
    - Boost leak test
    - Compression tested- Intake checked for blockages / MAF functioning
    - Actuated EGR and V719 flap with both removed to confirm movement and clean enough
    - Checked intake and clean enough
    - Injector deviations -1.29 / 0.5 / 0.5 / -1.27 (something like that but within spec) torsion value -0.5.
    - Timing has obv been physically confirmed in the beginning.
    - Swapped in a 2nd hand donor ECU i have.I should add the previous mechanic confirmed injector wiring loom with overlay harness and the car came to me with his diagnosis that the cam was worn (which i confirmed) and i have now changed with genuine Kolbenschmitt / bearings and lifters yet before and after symptoms remain unchanged with exception of injectors now being in spec (one of the injector lobes was visibly worn and outside tolerance and on removal bearings showing copper etc) but truth is this is not whats causing the main issue.

    I feel i have pretty much ruled everything out except injectors - i think.... but am getting so frustrated i cannot get a good positive fail on anything but obv i am missing something! Any fellow mechanics out there with an opinion please chime in as i need some fresh eyes on this. TIA.
     
    Last edited: Oct 30, 2015
  2. Keithuk

    Keithuk Super Moderator

    Joined:
    Aug 29, 2010
    Messages:
    7,026
    Car:
    2010 Golf GTD (170) CBBB
    Location:
    Stoke on Trent, England
    VAG Error Code: 16705/000801

    EOBD II Error Code: P0321

    Fault Location:
    Engine Speed Sensor (G28) - Implausible Signal

    Possible Cause:
    Malfunction Indicator Lamp (MIL)(K83) active.
    Engine shuts off.
    Engine doesn't start.
    Speedometer inoperative.
    Glow Plug Indicator Lamp (K29) flashes.

    Wiring/Connector(s).
    Engine Speed Sensor (G28) loose.
    Engine Speed Sensor (G28) faulty.

    Possible Solutions:
    Check/Replace all faulty Wiring/Connector(s).
    Check Engine Speed Sensor (G28).
    Read Measuring Value Blocks (MVB).

    Special Notes:
    The Engine Speed Sensor (G28) is also used as a reference sensor for the crankshaft position and correlates with the Camshaft Position Sensor Bank 1 (G40) and Camshaft Position Sensor 2 Bank 2 (G163).
    When found in a VW Golf/Jetta (1J/9M) or Audi A3 (8L) with 1.9l TDI-PD (AXR), check Technical Product Information (TPI) 2007067 which explains issues with electro magnetic interference. A modification to the wiring will fix this problem, extensive details can be found in the named Technical Product Information (TPI). Even though this Technical Product Information (TPI) was originally released for VW Golf/Jetta (1J/9M), a customer of ours came across the same issue on an Audi A3 (8L).
    When found in a 2004 VW Golf, Jetta, or New Beetle with 1.9l TDI-PD (BEW), check for Technical Service Bulletin (TSB) 2010461 (01-07-45 formerly 97-05-03) or 201463 (01-07-44 formerly 97-05-04) calling for a flash update to the Electronic Control Unit (ECU) and a secondary ground installation.
    VW Vehicles with the Most TSBs

    When is the code detected?:
    The P0321 code is triggered when the Engine Control Module (ECM) detects the signal is out of range.

    Description:
    Ignition failure sensor is used to check whether the spark ignition is occurred correctly or not and also used to tachometer drive. The sensor monitors the voltage difference between a resistance which is on the battery circuit for ignition coil. When the ignition coil works properly, the electric current through the resistance is detected as voltage drop. This is confirmed for every ignition event with the crankshaft sensor and the camshaft sensor. If Engine Control Module (ECM) detects a malfunction, no ignition is possible, so the engine would not start. If there is no ignition signal for a predetermined cycle for one or two ignition coils, an ignition coil circuit failure exists.

    As taken from my Free EOBD II Error Codes software
     
  3. 2012S3

    2012S3 New Member

    Joined:
    Apr 15, 2012
    Messages:
    9
    Car:
    2002 A3 Tdi (130PD)
    Thanks for that - i have stumbled across it before on the web but you did get me thinking again about the basic wiring.. Can anyone explain this. I thought i understood how the crank inductive sensor worked but this throws me. both are positive at the ECU (and the two right wires merge per diagram) yet with key on yet there is an an earth (132) on the same positive two right hand wires (bl / sw are clipped together and join li / gn to t60/43) Just cant make sense of it..
     

    Attached Files:

  4. Carlos-tj

    Carlos-tj New Member

    Joined:
    Oct 9, 2015
    Messages:
    28
    Car:
    2009 Bora TDI 1.9 BXE PD
    Location:
    Tijuana Mx
    OP:

    that injector deviation nimbers are very high. Usually more than 1.00 will have some driveability problem.

    Does your car have any mis-fire codes stored?
    Does it "nail" when pressing the accelerator? (Heavy pinging)
     
  5. 2012S3

    2012S3 New Member

    Joined:
    Apr 15, 2012
    Messages:
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    Car:
    2002 A3 Tdi (130PD)
    I scoped it again today with my new kit and after spending as much time figuring out the PC GUI got it set up and the wave form was clearly not right despite what the previous tech confirmed but mistakes happen so i am not gunning him. On 2nd visual inspection coming in at an angle via borascope i can now see 2-3 teeth are bent inward and as voltage increases at higer rpm so engine cuts as disparity amplified. Previously i borascoped perpendicular and thus could not see they were slightly bent. Sump off tomorrow, long mounted so will need subframe off if i can bend them back into shape otherwise its engine out. Fingers crossed as customer a good friend of mine.

    Next question is why they are bent. Its on its 3rd camshaft - soemthing will show in the sump altough one of the allen insert bolts shows rust like it has been removed before... hmm... Lets see.
     
  6. 2012S3

    2012S3 New Member

    Joined:
    Apr 15, 2012
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    Car:
    2002 A3 Tdi (130PD)
    Sump removed and bent 3 teeth back - you can make out 3-4 very slighly bent inward upto 1mm or there abouts. One of the rivets holding wheel to back of crank had sheared(also visible / rather the recess where the rivet end should be visible). Plan to put a very hot spot weld in to stop other end ever falling out, replace sump and check. Failing that it all starts getting rather more expensive.
     

    Attached Files:

  7. chittychittybangbang

    chittychittybangbang Administrator

    Joined:
    May 23, 2007
    Messages:
    23,901
    Car:
    2006 Jetta TDI
    Location:
    CT
    That would do it. I think those may be screws holding the wheel to the crank.
     
  8. 2012S3

    2012S3 New Member

    Joined:
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    Car:
    2002 A3 Tdi (130PD)
    not on this BPW engine - checked with a mirror but others VAG are screwed in. Perhaps if they were this wld not have happened. Its a ridiculous failure - spoken to many many VAG people over here and no one heard of it before but have heard of sender wheel 'moving' i suppose as bolts/rivets sheared. I really do not know why its not welded in place. I have best guessed teeth re-alignment as hard to do precisely at all let alone with sump off and subframe lowered but fingers crossed otherwise its new bottom end time.
     
  9. 2012S3

    2012S3 New Member

    Joined:
    Apr 15, 2012
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    Car:
    2002 A3 Tdi (130PD)
    It worked, car back up and running :)
     
    chittychittybangbang likes this.
  10. Keithuk

    Keithuk Super Moderator

    Joined:
    Aug 29, 2010
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    Car:
    2010 Golf GTD (170) CBBB
    Location:
    Stoke on Trent, England

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