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  1. #1
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    9-3 Convertible seat help requested

    Hello,

    I'm a custom car builder working on a 1948 Chevrolet street rod. I have power seats from a 2004 9-3 convertible that I'd like to use in this car. I have been unable to get them to operate properly and I'm looking for suggestions.

    These seats have memory and heat as well as power operation. I've been told that they need the signal from the -bus in order for them to work properly. I'd like to make them work without that if possible. Alternately, I'll look at a way to provide the I-bus signal to the seats. To do this I'm considering purchasing a DDM (driver door module) to see if that will provide the proper signal.

    I applied power to the main power and ground leads and the seat operates forward and backward, but not tilt or up/down. This tells me that power is getting through the control module to the motors, but I have not been able to determine why only the forward/back works.

    I have the wiring diagrams for the seats but I'll admit I'm no electric schematic expert. I suspect there may be a way I can bypass the control module and simply supply power to the switches. I would lose the memory function but that would be OK. When I recover the seats I'll cover over that spot in the seat.

    Any suggestions will be greatly appreciated. Thank you.

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  2. #2
    Saab Nut 9-3 Aero's Avatar
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    2009 9-3 2.0T SC Aero XWD\eLSD. eSID2
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    Hi,

    At the moment don't I have any firm suggestions, however could a description of which terminals/pins the power and ground leads were connected to, providing the forward and backward operation, materialize an idea.

    The challenge is, as you are well aware of, the missing signal from the ICM to the Driver's Seat Module (DSM), on the I-bus. The signal is pulse based (33 kbits/s), and as such not an easy task to duplicate - or cheat.

    Bypassing the DSM by patches would be the "quick fix" - if it wasn't for the fact that it provides the forward - and reverse polarity for the motors.

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  3. #3
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    Quote Originally Posted by 9-3 Aero View Post
    Hi,

    however could a description of which terminals/pins the power and ground leads were connected to, providing the forward and backward operation, materialize an idea.


    .

    Thanks, 9-3. Are you asking for a wiring diagram? I have that. I can attach if that would help with ideas.

    I will buy a CIM if there is a way I can get that to produce the required signal. I think a local Saab wrecking yard told me $200 for one of those. I paid $700 for the seats about 6 years ago. At this point I just want to get them working.

    One thing that puzzles me is why does forward and reverse work? It appears that motor does not need the I-bus signal, but I don't know why that would be. The Saab manual does not mention anything about that. I obtained copies of the relevant pages, diagrams, etc. from dealership here before they closed.

    Thank you

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  4. #4
    Saab Nut 9-3 Aero's Avatar
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    What would do, is just referring to connections made on your diagram, as I do have one (in the WIS).

    The CIM provides the "go" signal for the DSM, based on conditional inputs from other modules, this to inhibit adjustments of the seat when driving etc.

    The working actions puzzles me too, that's the reason for asking for the connections made.

    My (current) approach is to see if we can cheat the I-bus input to the DSM by providing a permanent "enable" of it.

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  5. #5
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    All I am doing is applying 12V to pins 37 (+) and 38 (ground) at connector H40-1. I figure the DSM must allow forward and backward adjustment all of the time but none of the others. It seems like the lumbar adjustment would work while driving as well but it does not work on mine.

    The pages I have out of the WIS tell me that the "comfort function" conditions must be met in order for the seat to be adjusted. It says comfort enable is primarily controlled by switch position. I would be perfectly happy if I could get that to be enable all of the time.

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  6. #6
    Saab Nut 9-3 Aero's Avatar
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    Thanks for the information provided. I still can't see why the forward and backward operation is working, but then there is NIL information given on how the DSM is programmed.

    My idea was to see if a "pull-down" or "pull-up" (resistor) on the I-bus input to the DSM could enable the module permanently. There are two challenges in that approach: the input is (most likely) edge triggered due to the pulsed messages, and the polarity of the pulses required to represent the "operate" signal for the DSM. A "0" (zero) is given by the pulse (on the bus) lifted towards +5V, and a "1" is interpreted by a pulse amplitude lower than 2.2V with reference to ground. My idea was to pull the I-bus input to DSM towards ground, however is a serie of "1" detected by the module as no messages being received.

    Given you want to give it a try the empirical way, with the potential risk of killing the DSM, I would need to have two measurements done when power is applied to the H40-1: multimeter positive probe on pin 23, I-bus, negative to pin 38, and the second one with positive on pin 23 and negative on pin 37 (confirm a negative sign).

    The lumbar system is independent with regard to bus communication and memory function, and should work by applying 12V to pins 24 (+) and 25 (ground).

    BTW: Is the seat belt tensioner's explosive charge still intact?

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  7. #7
    Saab Fan
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    OK, I'll get those readings for you next weekend. I have to go out of town for business in a few hours. And yes, everything is intact. I did not know there was a charge in the seat belt tensioner. My next step after getting them working was going to be removing the air bags. Sounds like there's one more obstacle to my use of these seats.

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  8. #8
    Saab Nut 9-3 Aero's Avatar
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    Then be careful with the charges, especially as you have disconnected plugs, being vulnerable with regard to (static) electrical discharge. There is a 10 meter safety zone recommended when the charges are to be disposed of by firing them.

    Good luck with the business trip

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    Last edited by 9-3 Aero; 29 June 2014 at 19:54. Reason: Spelling

  9. #9
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    OK, finally found time to try this. Going multimeter + to pin 23 and multi - to pin 38, I get no reading, all zeroes.

    From Multi + on 23 and - to piun 37 I did get a negative, 12.something.

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  10. #10
    Saab Nut 9-3 Aero's Avatar
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    Quote Originally Posted by 48builder View Post
    OK, finally found time to try this. Going multimeter + to pin 23 and multi - to pin 38, I get no reading, all zeroes.

    From Multi + on 23 and - to piun 37 I did get a negative, 12.something.
    As one last option, attempting to get the Saab seats electrically driven in the Chevy, you could see if the DSM gets "enabled" by fitting the R2 (1/4W) pull-down resistor as drawn on the "schematic".

    This is a cut-and-try method, as providing a DC signal to cheat a pulsed one really is questionable, due to the missing leading edges which are the "trigger" signals in the original setup. The I-bus is now, as measured by you, on a 12V+ level, whereas it switches between "0" and "1" when pulsed. A "1" is (as written in the other post) interpreted by a pulse amplitude (going) lower than 2.2V with reference to ground. The idea behind the resistor is to pull the DSM I-bus input towards ground, which could provide a "spike" when power is switched on. One of the challenges is however that a serie of "1" is detected as no messages being received.

    The idea is questionable and computation of the resistor is based on the little information found (in the WIS), however was the aim to get approx. +1,4V on the I-bus I/P, with reference to ground. The variables here are the design of the circuitry on the I/P, value of R1 (which could be 4Kohm) and charged / non charged 12V power.

    Given you would try this option - with the risk of frying the DSM - and the voltage measured pin 23 / - 38 of the H40-1 is above what is assumed, the value of the R2 resistor could be changed, thus to achieve a "1" .
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