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Thread: Level control faults - acceleration sensors

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    Level control faults - acceleration sensors

    Hi all,

    Tearing my hair out over here. Got a Bentley GT MY2010 with hard faults (all three acceleration sensors are open circuit/short to ground). So far have confirmed all power/grounds to the module okay; confirmed wiring from sensors to module okay and free of shorting; confrimed acceleration sensors are okay; confirmed level control module okay.

    I note the the 5V reference to the sensors is missing for each of them (it’s 1.4V out of the module and at the sensors). If I force this to 5V the respective fault code the clears.
    No idea what’s going on...smacks of module fault but it has been confirmed good.

    Any input be hugely appreciated.

    Code:
    Address 34: Level Control        Labels: None
       Part No: 3W0 907 553 B
       Component: LUFTFDR.-CDC- 3C3V0 7205  
       Coding: 0005561
       Shop #: WSC 00083 790 00000
       VCID: B93A7180F4FE118252-80EC
    
    3 Faults Found:
    00139 - Left Front Body Acceleration Sensor (G341) 
                009 - Open or Short to Ground
    00140 - Front Right Body Acceleration Sensor (G342) 
                009 - Open or Short to Ground
    00141 - Rear Body Acceleration Sensor (G343) 
                009 - Open or Short to Ground
    Last edited by deutschtech; 03-06-2019 at 04:35 PM. Reason: Added module scan in code tags

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  3. #2
    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by deutschtech View Post
    No idea what’s going on...smacks of module fault but it has been confirmed good.
    If the module is only producing 1.4V on an output where it's supposed to make 5.0V as a reference voltage, how can it be "confirmed good"?

    I don't have wiring diagrams for this thing handy, but is there just 1 pin from the module that the 5V reference voltage comes from, or is it three (one for each sensor)?

    -Uwe-
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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    Quote Originally Posted by Uwe View Post
    If the module is only producing 1.4V on an output where it's supposed to make 5.0V as a reference voltage, how can it be "confirmed good"?

    I don't have wiring diagrams for this thing handy, but is there just 1 pin from the module that the 5V reference voltage comes from, or is it three (one for each sensor)?

    -Uwe-
    Thanks for reply.

    I’ve tried other known good module on the car and same issue. For further verification I’ve install the module from this car on another identical vehicle and faults don’t follow.
    Each sensor is wired directly to the module via three wires (no intermediate connectors shown). Each sensor should have 5V on pin1.

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  6. #4
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    Sound like the 5 volt is being shorted to earth,

    Disconnect all level sensor and check 5 volt reference -
    If 5 volts is still no good check wiring for short earth
    If 5 volt ok - plug each sensor in until 1 by 1 until the 5 volt reference goes.

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    @DGMOTORS Many thanks for this. Your reply has just flagged that I’ve broken all the rules and missed the shorting tests (I’ll blame my tools - broken display in the tester). I’ll let you know how this goes.

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    NostraJackAss Jack@European_Parts's Avatar
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    Sound like the 5 volt is being shorted to earth,

    Disconnect all level sensor and check 5 volt reference -
    If 5 volts is still no good check wiring for short earth
    If 5 volt ok - plug each sensor in until 1 by 1 until the 5 volt reference goes.
    Excellent recommendation and if still is observed after aforementioned you should isolate the module and power up or on bench to see if the 5 volt ref wakes up than isolate other circuits that could be causing a brown out too of controller before replacement.
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    FIXED. Was an internal partial short to ground on the 5V reference in one of the front acceleration sensors. As the circuit diagram shows the sensors are all wired independently I hadn’t factored in that inside the module they could be connected. So one sensor pulled the whole lot down, flagging the codes in my OP. Interesting that a single faulty unit throws codes condemning the whole bunch of them (makes perfect sense electrically, now I know the setup inside the mysterious “black box”).

    Thanks again to all who contributed, @DGMotos in particular (own you a beer for the fresh-eyes on this one mate).

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  13. #8
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    No worries,

    It all fixed is the main thing.

    Next time I'm in MK i'll call in for my beer! (Only joking and guessing you are the Milton Keynes garage)

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