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Cadillac STS Forum - 2005 through 2012 Discussion, MRC Diagnostic help in Past Cadillac Vehicle Discussion; I have replaced three of the struts in my car. Passenger front was leaking and was replaced by service contract. ...
  1. #16
    Ludacrisvp's Avatar
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    I have replaced three of the struts in my car.

    Passenger front was leaking and was replaced by service contract.

    Driver front was replaced a couple months later due to leaking by service contract. At the same time the front passenger was replaced again due to leaking again this time replaced under GM part warranty.

    Driver rear was recently replaced (out of pocket) due to leaking.

    Carvone - it's somewhat nice to know that I'm not the only one that has seen an issue like this.

    1BadCadSTS - it would be nice if I could figure out for sure what is actually wrong. Is it the suspension control module? Is it wheel speed sensors? Is it one of those white caps?

  2. #17
    1BadCadSTS's Avatar
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    Suspension module is in the trunk passenger side mounted on the wheel well.

  3. #18
    ewill3rd is offline Cadillac Technician
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    Re: MRC Diagnostic help

    The shocks/struts on this model appear to be set up for Road Sensing Suspension (RSS).
    Vehicle top speed is by design and set by vehicle equipment including suspension and tire specifications.
    RSS doesn't have anything to do with speed limiting although I belive if RSS sets a code it CAN set a lower limit than the vehicle's pre-set top speed.

    I work as a dispatcher/advisor at a GMC/Buick Dealer in Woodbridge, VA now.
    Miss you guys.
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    RippyPartsDept likes this.

  4. #19
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    Re: MRC Diagnostic help

    Quote Originally Posted by ewill3rd View Post
    The shocks/struts on this model appear to be set up for Road Sensing Suspension (RSS).
    Vehicle top speed is by design and set by vehicle equipment including suspension and tire specifications.
    RSS doesn't have anything to do with speed limiting although I belive if RSS sets a code it CAN set a lower limit than the vehicle's pre-set top speed.

    I work as a dispatcher/advisor at a GMC/Buick Dealer in Woodbridge, VA now.
    Miss you guys.
    Lead a busy life these days.
    Thanks for looking at this.

    The manual page 3-93 or 247 lists the following:
    "SPEED LIMITED TO XXX"
    'This message displays when the vehicle speed is limited to XXX, mph in English mode and km/h in Metric mode, because the vehicle detects a problem in the steering, stability control, or suspension system. Have your vehicle serviced by your dealer/retailer. '


    Based on the equipment my car came with I believe that my vehicle top speed should be set to 149/155 area based on tire speed ratings of the OEM tire being rated for 168+mph.
    My main goal is to resolve whatever the underlying issue is that is causing it. I don't like having a car that has potentially faulty systems in it.
    Is there any type of reference chart to show what MPH limit is set means certain failures / typical causes?
    I've seen members mention theirs showing SPEED LIMITED TO 155MPH, mine has done SPEED LIMITED TO 120MPH, and when disconnecting shocks I can force it to SPEED LIMITED TO 80MPH.
    So my logic is that certain conditions cause certain limits to be set.

    All the dealers I've gone to are more concerned with me wanting to go faster than 120MPH, honestly I don't care that much about the limit. I don't like having faulty equipment, and if the car is lowering its top speed for safety concerns I feel that it should be something that can be fixed.

    I've only focused on the suspension since I've replaced 3 of the shocks so far due to leaking fluids and it seemed like bad shocks were the most common cause for issues in the 2002.5-2004 seville w/ F55 MRC when there was a speed limited message involved.

  5. #20
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    Re: MRC Diagnostic help

    Quote Originally Posted by ewill3rd View Post
    The shocks/struts on this model appear to be set up for Road Sensing Suspension (RSS).
    Vehicle top speed is by design and set by vehicle equipment including suspension and tire specifications.
    RSS doesn't have anything to do with speed limiting although I belive if RSS sets a code it CAN set a lower limit than the vehicle's pre-set top speed.

    I work as a dispatcher/advisor at a GMC/Buick Dealer in Woodbridge, VA now.
    Miss you guys.
    Lead a busy life these days.
    Good to hear from you again. Congratulations on your new position. Thanks again for being very helpful to me when I first joined this forum.

    Doug

  6. #21
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    Re: MRC Diagnostic help

    A PC program known as "Autoenginuity", when used with their USB adaptor will read out body and suspension codes for you as well as ECM, heater, and ABS. It's a hell of a lot cheaper than a TEC 2 and might help you get some insight on your problem. What you really need to know is what specific fault generates the 120MPH fault message. I'm guessing it's some artifact left over from engineering testing at GM that wasn't properly disabled and has become a ghost possibly triggered by a bad ground or other random system noise fault. Somebody somewhere in GM knows but they ain't saying.
    Don't mess with Binky Bear!


  7. #22
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    Re: MRC Diagnostic help

    Quote Originally Posted by dkozloski View Post
    What you really need to know is what specific fault generates the 120MPH fault message. I'm guessing it's some artifact left over from engineering testing at GM that wasn't properly disabled and has become a ghost possibly triggered by a bad ground or other random system noise fault. Somebody somewhere in GM knows but they ain't saying.
    It is also possible that while someone somewhere in GM does know the answer but they aren't anywhere close to a customer facing position and they likely have no idea that this is an issue somewhere.

    Precisely what I'm looking for is / are the possible faults that can yield the 120MPH message, then eliminate potential causes one by one.

    Now perhaps its not that easy as it may not be defined how we are thinking / assuming it is.
    It may not be if code XXXX is present then limit speed to YYY, its possible that it is like if code XXXX is present then reduce speed limit by YYY from set limit ZZZ.

    So potentially it could be if a certain code is present reduce limit by 10MPH, if another certain code is present then reduce by 5MPH so when active together it reduces your limit by 15MPH. (trying to better explain my theory).

    I did try and look at the module in the trunk, interesting design, its basically a flat plate of metal with a plug on it, honestly not sure how it is large enough to even have a circuit board in it, and the connector that is plugged into it didn't appear to be very easy to unplug to get a better look at it.

  8. #23
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    Modules cake to unplug. I swap back and forth between two modules for testing madtuner suspension cals.

  9. #24
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    Re: MRC Diagnostic help

    Business is slow today so I am looking to pass some time
    You are welcome by the way, I have always enjoyed offering advice and helping whenever I can. Maybe I need to do it more, I have been kind of in a funk lately.

    Bottom line, the speed limiting is a function of the ECM. I don't think it is hard coded in the module, but likely software coded. The only thing I could think of would be to calibrate the car with software for a VIN that will run the higher limit.
    GM calibrations are based on equipment as manufactured and they programmed the limit into it.
    The next issue would be to reset other modules to have the updated VIN and match security information for proper starting and operation.
    To me it isn't worth the effort, all fuel injected cars have limiters built into them, even motorcycles. Without being able to edit the calibrations yourself I don't know of another way to reset the speed limiter.

  10. #25
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    Re: MRC Diagnostic help

    Bill

    Luda more so is asking what kind of failure would cause a speed limited to 120 message to pop up.

    On older CVRSS systems if a strut had failed or one of the ride height sensors it would trip a service suspension sys message and speed limited to 90.

    His car has had an undiagnosed problem which will cause this DIC to flash Speed Limited to 120. No codes have been stored and I believe the dealer let him borrow an screen shot tool and still they have been unable to provide a cause.

    They initially blamed his lock pick and iPod interface as the issue saying it was broadcasting a signal over the LAN system tripping the fault. He now has them both removed and still has the issue.

    Do you know what issues (such as a short to the EBCM or a bad compressor etc) that would cause the Speed Limited specifically to 120 MPH to occur on his car?

  11. #26
    Ludacrisvp's Avatar
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    Bill I sincerely do appreciate your assistance.
    1BadCadSTS is correct on all counts of the situation. If you were to google this forum for my username and speed limited to 120mph you'd find a lot of fun threads around it. Lol.

    I am 99% certain that the EBCM (located in the passenger side dashboard) was replaced twice actually. Once with a bad replacement that was already programmed for a different car when it arrived causing all sorts of issues. I'd have to look through the 2 dozen or so service calls on the car to find the part number used and the exact reason they decided to swap it out.

  12. #27
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    Luda


    I'm going to a bone yard this weekend. Let me ass if I can grab a suspension module for you to try. While the vin is programmed into it they are not vin locked and can be run on any STS provided its the same system (fe1 fe3 etc). If the code doesn't come back there's your issue.

  13. #28
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    Quote Originally Posted by 1BadCadSTS View Post
    Luda


    I'm going to a bone yard this weekend. Let me ass if I can grab a suspension module for you to try. While the vin is programmed into it they are not vin locked and can be run on any STS provided its the same system (fe1 fe3 etc). If the code doesn't come back there's your issue.
    That would be sweet. Let me know if you need my RPO sticker or not. (It should be posted in one of my threads I believe.)

  14. #29
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    I have no idea how see became ass in my previous post hahaha.

    As long as your mrc awd your fine. I know they had a wrecked 05 awd with mrc as it had 18s there's another black 06 awd but it had 17s so not sure if it did or didn't.

  15. #30
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    Re: MRC Diagnostic help

    Yeah, AWD w/ MRC.

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