Memory Seat seems to reset itself differently every so oftn
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Cadillac Seville / Cadillac Eldorado Forum Discussion, Memory Seat seems to reset itself differently every so oftn in Past Cadillac Vehicle Discussion; I started using the memory seat option on my "new" 99 ETC after replacing a fuse that kept it from ...
  1. #1
    SissyBoyFloyd's Avatar
    SissyBoyFloyd is offline Cadillac Owners Member
    Automobile(s): 99 Eldorado ETC
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    Memory Seat seems to reset itself differently every so oftn

    I started using the memory seat option on my "new" 99 ETC after replacing a fuse that kept it from working. Read manual about how it works and set it accordingly. It set fine and worked fine the first few days. Both the Exit setting and driving setting worked. Then a couple days this last week, I got in and the seat didn't set fully to drive but still set right when Exiting. I reset it and it worked fine again, but today seemed to lose its setting again. I reset it again, and it works fine now.

    Any clues to why it does this? I can live with it like this, but would love to know why its doing it. I first thought that it must have kept its old setting and wondered if there was a way to make sure all old settings are erased from its memory for good.

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  3. #2
    dou1t2 is offline Cadillac Owners Member
    Automobile(s): 96 Seville SLS and 99 Eldorado ESC,also 91 F-150 and a 73 MG
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    Re: Memory Seat seems to reset itself differently every so oftn

    I have the same problem at times with my newly acquired 99 ESC, but I think it has do with my stereo being removed and an aftermarket installed. It shows erratic behavior at times. Like the driving lights flashing upon starting the car, I just turn the headlights on and it is solved. The passenger mirror will readjust it self at times. The trip meter resets itself, even if I don't hit the button. It apparently is caused by turning car off and sitting for 18 to 20 hrs. I drive it daily, and learn a new quirk daily almost!

  4. #3
    rodnok01's Avatar
    rodnok01 is offline Cadillac Owners Connoisseur
    Automobile(s): 98 DeVille, 97 DeVille d'Elegance
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    The BCM controls those options. My 98 DeVille will do strange things sometimes when using key fob.
    Before chaning BCM sometimes seat would move to flat when you hit #1...
    Personally I think these have some quirks and you are experiencing them.

  5. #4
    N*Caddy's Avatar
    N*Caddy is offline Cadillac Owners Master
    Automobile(s): 1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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    Re: Memory Seat seems to reset itself differently every so oftn

    Actually the BCM (in our cars called PZM) has NOTHING to do with the memory settings, it does not even listen to the driver no message on the data line.
    The modules listening and acting on this message are:
    MMM - Adjusting the mirrors
    MSM - Adjusting the seat
    HU - Adjusting the audio settings
    CCM - Adjusting the climate settings

    There are 2 modules broadcasting the message on the data line (but not acting on it):

    RFA - Broadcasts to the above modules what remote was used (thus what driver number is to be selected)
    IPC - Broadcasts to the above modules what button was used to recall the settings
    Also the IPC broadcasts to the MSM when the user pressed the memory buttons to store the position.

    What the OP has is an issue with one of the position sensors for the seat, you will find a code for it (at least in history). When you use your remote the RFA broadcasts to all modules select driver X (based on what was set on the RFA as remote for driver 1 or 2).
    Let's focus on the seat. The MSM receives the message and will compare the reading from all the seat position sensors (1 for every 2 movements, example Up/Down uses one sensor so do Forward/Backward...) anyway, the MSM has in its memory the position (reads a Voltage) of each sensor.
    Say one sensor reads a voltage higher than the stored position, well in this case the MSM will apply power to the appropriate motor and with the polarity to induce a movement that will move the seat in the direction the sensor output voltage is decreased. It will cut the power to the motor in the moment when the sensor readout will match the stored value.
    Now the sensor has a voltage between x and y volts where x is greater than 0V (there is a minimum voltage) and Y is less than 12V (there is also a maximum voltage). An educated guess will tell me it operates somewhere between 3V and 8V. The reason is not operating between 0V and 12V is so the MSM can figure out when there is an issue with the sensor (< than minimum voltage = Short to Ground and > maximum voltage = Short to battery).
    The sensor is nothing but a potentiometer with a maximum resistance of ~15K Ohms and minimum few hundred Ohms. As any potentiometer in time will fail (either wearing out the resistive film, or what ever other failure). So instead of having a continuos variation from min to max may have portions where the resistance jumps up and down. It may jump but not enough to go over the min/max values when the MSM will pick it up as a bad value so now your MSM will just try to adjust based on wrong information sent by the defective sensor.

    So if you have no code you can still figure out what sensor is at fault by simply paying attention to what movement gives you issues. If the seat moves forward or backward then that sensor defective. Normally most people use this movement the most so this is the sensor most prone to have issues.

    To access the sensors you need to move the seat all the way forward and all the way UP (rear of the seat).
    Then access the 2 T (not sure what size) in the back of the seat rails. That's what holds the seat bolted to the car.
    Now you can lift the rear of the seat (not too much) to disconnect the harness coming from floor to the seat.
    With the harness disconnected pull the seat ~1 inch back (rear lifted) and the seat is free, can be removed from the car.
    All the parts of your interest are on the bottom of the (rather heavy) seat.


    The MSM module had an “advanced” diagnose mode using the car chimes. Basically there is a service port that needs to be grounded on the MSM connector and you can use the buttons and listen to chime pattern for various diagnose, basically the MSM is commanding on the data line to the HU to produce fast or slow chimes that have a certain meaning (is all described in the FSM). That in case the codes are not enough.

  6. #5
    basscatt's Avatar
    basscatt is offline Cadillac Owners Master
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    Re: Memory Seat seems to reset itself differently every so oftn

    Quote Originally Posted by N*Caddy View Post
    Actually the BCM (in our cars called PZM) has NOTHING to do with the memory settings, it does not even listen to the driver no message on the data line.
    The modules listening and acting on this message are:
    MMM - Adjusting the mirrors
    MSM - Adjusting the seat
    HU - Adjusting the audio settings
    CCM - Adjusting the climate settings

    There are 2 modules broadcasting the message on the data line (but not acting on it):

    RFA - Broadcasts to the above modules what remote was used (thus what driver number is to be selected)
    IPC - Broadcasts to the above modules what button was used to recall the settings
    Also the IPC broadcasts to the MSM when the user pressed the memory buttons to store the position.

    What the OP has is an issue with one of the position sensors for the seat, you will find a code for it (at least in history). When you use your remote the RFA broadcasts to all modules select driver X (based on what was set on the RFA as remote for driver 1 or 2).
    Let's focus on the seat. The MSM receives the message and will compare the reading from all the seat position sensors (1 for every 2 movements, example Up/Down uses one sensor so do Forward/Backward...) anyway, the MSM has in its memory the position (reads a Voltage) of each sensor.
    Say one sensor reads a voltage higher than the stored position, well in this case the MSM will apply power to the appropriate motor and with the polarity to induce a movement that will move the seat in the direction the sensor output voltage is decreased. It will cut the power to the motor in the moment when the sensor readout will match the stored value.
    Now the sensor has a voltage between x and y volts where x is greater than 0V (there is a minimum voltage) and Y is less than 12V (there is also a maximum voltage). An educated guess will tell me it operates somewhere between 3V and 8V. The reason is not operating between 0V and 12V is so the MSM can figure out when there is an issue with the sensor (< than minimum voltage = Short to Ground and > maximum voltage = Short to battery).
    The sensor is nothing but a potentiometer with a maximum resistance of ~15K Ohms and minimum few hundred Ohms. As any potentiometer in time will fail (either wearing out the resistive film, or what ever other failure). So instead of having a continuos variation from min to max may have portions where the resistance jumps up and down. It may jump but not enough to go over the min/max values when the MSM will pick it up as a bad value so now your MSM will just try to adjust based on wrong information sent by the defective sensor.

    So if you have no code you can still figure out what sensor is at fault by simply paying attention to what movement gives you issues. If the seat moves forward or backward then that sensor defective. Normally most people use this movement the most so this is the sensor most prone to have issues.

    To access the sensors you need to move the seat all the way forward and all the way UP (rear of the seat).
    Then access the 2 T (not sure what size) in the back of the seat rails. That's what holds the seat bolted to the car.
    Now you can lift the rear of the seat (not too much) to disconnect the harness coming from floor to the seat.
    With the harness disconnected pull the seat ~1 inch back (rear lifted) and the seat is free, can be removed from the car.
    All the parts of your interest are on the bottom of the (rather heavy) seat.


    The MSM module had an “advanced” diagnose mode using the car chimes. Basically there is a service port that needs to be grounded on the MSM connector and you can use the buttons and listen to chime pattern for various diagnose, basically the MSM is commanding on the data line to the HU to produce fast or slow chimes that have a certain meaning (is all described in the FSM). That in case the codes are not enough.
    -------------------------------------
    EXCELLENT explanation -

    N*Caddy is our resident Electrical Engineer -
    he has CRAZY skills when it comes to the electrical system of a Caddy -

    his 97 STS is definitely a ONE-OF-A-KIND -
    with features and options from later models -
    unavailable to "MORTAL MEN" -

  7. #6
    SwampeastMike is offline Cadillac Owners Enthusiast
    Automobile(s): 99 STS, White Diamond
    Join Date
    Nov 2008
    Location
    Cape Girardeau, Missouri
    Age
    50
    Posts
    778

    Re: Memory Seat seems to reset itself differently every so oftn

    Try pressing and holding the "1" or "2" memory recall button when things don't go to the proper position. If pressing and holding gets everything to move to the proper position then there is no sense looking for an physical or electrical problem. This seems to be a "normal" problem that problem that happens on occasion.

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