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U0020 DTC Code

Discussion in 'Engine & Drivetrain' started by YukonXLMan, Jul 16, 2019.

  1. YukonXLMan

    YukonXLMan Member

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    I ran a new diagnostic tool I purchased today and it shows that all is well EXCEPT a U0020 Low Speed CAN Communication Bus Performance error. I'm not having much luck locating what this might mean on my 2017 Yukon XL SLT. I'm not experiencing any symptoms that I'm aware of. Might anyone have some insight they can provide on this? Thanks!
     
  2. Rocket Man

    Rocket Man Build It Better Supporting Member

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    Is it a history or current code? Might have been just a one-time thing that needs to be erased.
     
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  3. YukonXLMan

    YukonXLMan Member

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    Thanks for the response. it was the first scan I've done on the auto, so unclear as to how long/current the code has been. I did clear it and will check again this weekend.
    The code showed up under the Steering Column Lock Control Module--didn't know I had a module for it!
     
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  4. Rocket Man

    Rocket Man Build It Better Supporting Member

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    The new trucks have more computer modules than you would believe. All gathering data on you and sending it to GM. More data than you can imagine. The news just had some reporting on this, pretty scary stuff.
     
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  5. dwchapmanjr

    dwchapmanjr TYF Newbie

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    The computer stores codes as active, pending or history. At a high level, active means it is actively alerting on your current drive cycle. Pending means it may take 2 cycles for a DTC to show up on the dash and history means its an old code that is none of the above.

    The formatting on mine is terrible but notice mine says "DTC Current Status: Current". I did a full scan once before and didn't get this but it did have some problems reading all the modules last time I did it and this time it went through them all.

    Mine is a 2015 GMC Yukon so I imagine this is likely not uncommon of a code and likely doesn't throw a dash light. Interestingly this module uses the low speed CAN.

    In my case I cleared it and it was the only module alerting at the time. We'll see if it comes back.

    U0020.jpg
     
  6. swathdiver

    swathdiver Full Access Member

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    DTC Descriptor
    DTC U0020 00
    Low Speed CAN Communication Bus Performance
    Circuit/System Description

    Modules connected to the GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have programmed information about what messages are needed to be exchanged on the serial data circuits. The messages are also supervised and some periodic messages are used by the receiver module as an availability indication of the transmitter module.

    DTC U0020 will set when fewer modules are detected on the bus before the modules can learn the other modules IDs. If the communication bus is opened, or if the modules power supply is lost when the vehicle is in the OFF power mode, and then placed in the RUN power mode, U0020 will set in specific modules.

    Conditions for Running the DTCs

    Voltage at the modules is in the normal operating voltage range.
    The vehicle power mode requires serial data communication to occur.
    The DTC U2100 does not have a current status.
    Conditions for Setting the DTC

    A supervised periodic message that includes the transmitter module availability has not been received.

    Action Taken When the DTCs Sets

    The module uses a default value for the missing parameter.

    Conditions for Clearing the DTC

    A current DTC clears when the malfunction is no longer present.
    A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.
     
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