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Thread: U1016

  1. #31
    Joe (Moderator) joecar's Avatar
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    EBCM = electronic brake control module (aka ABS).
    BCM = body control module

    Unfortunately, on F-body the BCM is not on the Class 2 bus.

    Keep probing... you will find it.

    You can also run one module on the bus at a time... see if one module in particular causes DTC's to pop up.

  2. #32
    Lifetime Member mr.prick's Avatar
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    Quote Originally Posted by joecar View Post
    EBCM = electronic brake control module (aka ABS).
    BCM = body control module

    Unfortunately, on F-body the BCM is not on the Class 2 bus.

    Keep probing... you will find it.

    You can also run one module on the bus at a time... see if one module in particular causes DTC's to pop up.
    this conflicts with what i was told by Blacky.....

    Quote Originally Posted by mr.prick
    am i correct to assume the BCM is part of the IPC?
    on the class-2 com.

    Quote Originally Posted by Blacky
    Yes, the BCM communicates on the class-2 network.

    When network codes get set a fair amount of "default" value processing goes on in the PCM. Basically after a network fault code, the PCM "distrusts" data from other modules and substitutes default values for some or all of them. So I am not surprised at a poor performing engine if the PCM has network codes. I don't think the poor performance is caused by any physical fault, just the PCM dumbing itself down due to the network errors (but I could be wrong). The network errors could be caused by faulty loom, connectors or even a faulty module dragging the whole bus down with it.

    The reason I mentioned high speed mode is that you said you could read codes etc but could not read/flash. The only time high speed mode is used is when reading/flashing which is when you say it fails. So I was trying to think of what was different between just reading codes (at 1x speed) and reading/flashing (at 4x speed).

    If the class-2 network is flaky and has some short or open circuit even intermittently, then it will be magnified during high-speed read/write because the VPW transceivers switch off their wave shaping filters during high speed mode, so the tolerance to interference will be lower.

  3. #33
    Joe (Moderator) joecar's Avatar
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    Default F-body is different --> "special"

    Lol......all other car models are different than F-body...

    F-body BCM is not connected to the Class 2 bus, and has no bus style connection to any other module...

    (this makes it a PITA to diagnose BCM problems, as you have discovered)

    See attached diagrams (All Else.zip and PCM.zip) for 2001/2002 F-body.

    Even the high end Genisys/Snap-On scantools do not see the BCM when connected to the F-body DLC...

    By contrast, Y-body has just about everything on the Class 2 bus, see attached... ...it's a wonder that the tunetool can get bus bandwidth.

    So Paul was correct about the BCM being on the Class 2 bus, for everything except F-body...
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  4. #34
    Lifetime Member mr.prick's Avatar
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    it`s not "on the bus", but is`nt it part of the IPC?

    i am suspecting the BCM mostly because of the P1626
    as well as all the Uxxx codes.

    i was also hoping for an easy fix.

    also something very odd now,
    i removed the radio an was able to start the car and it stayed running,
    but flashscan could still not connect.
    after 3 starts the car is once again in a non start/running state.
    this is most likely a fluke.
    Last edited by mr.prick; September 10th, 2008 at 11:04 AM.

  5. #35
    Joe (Moderator) joecar's Avatar
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    Default F-body only

    Quote Originally Posted by mr.prick View Post
    it`s not "on the bus", but is`nt it part of the IPC?
    The BCM is not on the bus, and it's not part of the IPC... it's all by itself...

    See the diagrams for BCM and IPC.

    The IPC is located in front of driver;
    The BCM is located in passenger side footwell;

    The BCM illuminates the following LEDs on the IPC display (the dash):
    - Seat Belt,
    - Security

    And it also illuminates the Theft/Alarm LED on top of the dash.

  6. #36
    Joe (Moderator) joecar's Avatar
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    Ok, I reread your post #1:
    - getting fuel,
    - not getting spark;

    Post #34: removed radio and motor started, but won't run after 3 starts...

    I assume starter cranks ok each time.


    Check with scantool that PCM's fuel enable state is on and VATS state is off...
    i.e. is PCM not fueling dues to VATS/BCM theft reason (are you having key pellet trouble...?)...?

    Verify that you are getting fuel (I'm assuming so).
    Verify that you are not getting spark (I'm assuming not).

    Do you have a LED test light (i.e. uses red/green LED instead of a light bulb)...?
    This draws low current which prevents damaging the PCM's internal sources/sinks;
    Get one from local parts store;

    Refer to coil diagrams in PCM folder I posted above...

    If no spark, then coils are not firing...
    disconnect coil primary and with key on check:
    - battery voltage between pins D and A;
    - zero (or almost zero) volts between pins B and A;
    If those fail, then there is a grounding problem or a PCM with dead sources/sinks;

    then while cranking, check:
    - voltage "signal" between pins C and B using LED test light;
    If that fails, then must determine why there is no coil trigger signal (go upstream)...
    open/short circuit, or grounding problem;

    If those all pass and you get this far, then something's wrong with the coils or grounding or spark plugs/wires.

  7. #37
    Lifetime Member mr.prick's Avatar
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    Quote Originally Posted by joecar View Post
    Ok, I reread your post #1:
    - getting fuel,
    - not getting spark;

    Post #34: removed radio and motor started, but won't run after 3 starts...

    I assume starter cranks ok each time.


    Check with scantool that PCM's fuel enable state is on and VATS state is off...
    i.e. is PCM not fueling dues to VATS/BCM theft reason (are you having key pellet trouble...?)...?

    Verify that you are getting fuel (I'm assuming so).
    Verify that you are not getting spark (I'm assuming not).

    Do you have a LED test light (i.e. uses red/green LED instead of a light bulb)...?
    This draws low current which prevents damaging the PCM's internal sources/sinks;
    Get one from local parts store;

    Refer to coil diagrams in PCM folder I posted above...

    If no spark, then coils are not firing...
    disconnect coil primary and with key on check:
    - battery voltage between pins D and A;
    - zero (or almost zero) volts between pins B and A;
    If those fail, then there is a grounding problem or a PCM with dead sources/sinks;

    then while cranking, check:
    - voltage "signal" between pins C and B using LED test light;
    If that fails, then must determine why there is no coil trigger signal (go upstream)...
    open/short circuit, or grounding problem;

    If those all pass and you get this far, then something's wrong with the coils or grounding or spark plugs/wires.
    the starter cranks,
    i`ve logged GM.STATE02 and VATS is inactive,
    GM.STATE14 all coils ok
    i pulled plug #2 and it was a little wet.
    WBO2 AFR was quite lean though.
    remember the car lopes badly so data maybe skewed.

    would on open ANYWHERE on the car cause the
    non connection problem?
    like a tail/headlight.

    the fact i can`t read/flash the stock PCM but log PIDs and DTCs
    was explained by blacky via PM
    Quote Originally Posted by mr.prick
    i cannot connect through the OBDII (DLC) port to
    flash/read the PCM. (stock PCM)
    i can scan DTCs and PIDs though.

    i have checked all fuses, the serial connector (star)
    PCM, and DLC for continuity

    is there anything else that can look into
    that is causing this disruption in the serial com?
    can a failed module (IPC, EBCM and SDM)
    cause this?

    thanks
    Quote Originally Posted by Blacky
    If it is a CAN based vehicle then I cant think of anything, but if it is a VPW based vehicle, then chances are one or more modules are failing to honor the high speed read/program mode. If just one module does not honor the high-speed mode then it can cause faults on the entire class-2 bus.
    Quote Originally Posted by Blacky
    4.1.5 4X Mode
    4X mode is entered when the host loads the 4X mode bit configuration into the configuration
    byte.
    During 4X mode, transceiver waveshaping is disabled, thus allowing the DLC to operate
    without any slew rate limitation. 4X mode affects only the transmitted and received
    symbol timing logic of the DLC (including the digital filter).
    4X mode allows communication on the multiplex bus to be performed at four times the
    normal bit rate.
    This high speed transfer function does not work properly unless all transmitting nodes
    on the J1850 bus are in 4X mode. Selected receivers may be configured to ignore high
    speed frames until a BREAK symbol is received. Detection of a BREAK symbol on the
    J1850 bus returns the DLC to normal mode.
    all the hot and grounds that i`ve checked have been audible
    all the way to the battery cables.
    i hope this is the correct way to do this. (battery disconnected)
    i figure that if i get an audible all the way to the very end of the source of power/ground than there is no open anywhere.
    also i have checked each module`s to serial connector (star) wires
    also the PCM to 12volt/ground, fuel enable and, DLC (obd2 port)

    the BCM seems to be working, i.e
    i can program the alarm and all the wires have the right voltage
    and i hear the relays click.
    but once the car dies or i switch the ignition off i can
    hear the fuel pump "re-prime".

    is there any way to test any of the modules with flashscan?

  8. #38
    EFILive Developer Site Admin Blacky's Avatar
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    Quote Originally Posted by mr.prick View Post
    this conflicts with what i was told by Blacky.....
    Sorry, my bad. I made a big, bad, wrong assumtion - go with what Joe says.
    Paul
    Before asking for help, please read this.

  9. #39
    Joe (Moderator) joecar's Avatar
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    Also log GM.VATS.

    Disconnect all 4 modules from bus (PCM, EBCM/ABS, IPC, SDM), and reconnect one at a time... each time, cycle ign key, connect scantool and see if U1016 pops up...
    it seems to me that U1016 is posted by whichever module is trying to get on the bus but is not able to dues to another module hogging it.

    I don't like the ohms/continuity test because it draws very little current... some bad connections seem ok when passing low current, but fail with larger current (the voltage drop is larger with larger current... V=I*R)...

    With DMM set on 20VDC scale,
    with batt. connected,
    place DMM neg. probe on batt. neg.,
    with DMM pos. probe check that:
    - all hot nodes read close to battery voltage;
    - all gnd nodes read close to zero volts;
    Post your readings.

  10. #40
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by Blacky View Post
    Sorry, my bad. I made a big, bad, wrong assumtion - go with what Joe says.
    Paul
    lol... ... F-body is different in various ways... even the chassis is asymmetrical left-right... it's an engineering wonder it tracks in a straight line...

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