Passive Strut Mystery

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Suspension, Brakes and Tires Discussion, Passive Strut Mystery in Item Specific Cadillac Discussion; Hi guys, I feel kind of bad to post a question about "Service Ride Control" since it's been discussed ad ...
  1. #1
    JN in CA is offline Cadillac Owners Member
    Automobile(s): 1994 Diamond ETC N*
    Join Date
    Nov 2007
    Northern California

    Passive Strut Mystery

    Hi guys, I feel kind of bad to post a question about "Service Ride Control" since it's been discussed ad nauseum, but I've read through a bunch of threads here, and I cannot get this one fixed.

    The car is a '94 ETC with RSS, and we put in passive struts. I took it to an auto electrical shop that recommended these because it has installed these several times before, and never had a problem. They cannot solve this one.

    In the shop, no error, but as soon as the test drive hits a really bumpy patch of pavement or gets to freeway speed, (I presume that's when the normal struts would stiffen, but I don't know that) the "Service Ride Control" light comes on, with the usual s012 s013 s017 s018 etc. codes for the struts.

    They have tried resistors from 2 ohm up to over 5000 ohm, even a variable resistor that goes to over 10k ohm, and it is always the same. I've printed out some of the instructions on here and taken it into them, but nothing has worked. They replaced the ride computer (not that I thought that was the problem, but I guess it's nice to cross it off the list of suspects) and it didn't help. If anyone has an idea what's wrong, I'd appreciate any clues.

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  3. #2
    Krashed989's Avatar
    Krashed989 is offline Cadillac Owners Connoisseur
    Automobile(s): 94 Eldorado, and a 99 ETC
    Join Date
    Sep 2004
    Hilo, Hawaii

    Re: Passive Strut Mystery

    The computer is not looking for a resistance. It's looking for a sort of latency in the current from inducing a magnetic feild in the solenoid on the shocks/struts. Instead of using a resistor, try using an electromagnetic coil. (that worked with mine).... If you were to hook up a speaker to where the solenoid is, you will get a lound noise as you drive over bumps (an electric frequency is being sent to the solenoid). What the coil does is smooth this frequency out and a steady (or close to steady current) is analyzed by the computer. If the coil is not functioning properly, it wont smooth the frequency out (and it will do the same thing as a resistor) and the computer will think something is wrong.

    Why does the coil smooth the frequency out? Because it takes energy to induce the magnetic field (basically charging it up similar to a battery). So each pulse of electricity first charges the magnetic field and then leaks out (at a certain rate, depending on the amount of charge and the size of the coil) to go on its way to the computer.... The same idea as adding water to a bucket with a hole in the bottom; you can pulse the water you add to fill up the bucket (creating the magnetic field), but still a steady stream of water will come out of the hole..... The problem with the resistor is that it's too instantaneous. All it does is convert voltage to amperage, so you still end up with a frequency in the end.

    I think 96 is when they switched the computer to looking for resistance instead. Muuuuuuuch simpler and easier to diagnose (and jimmyrig.. haha)

  4. #3
    stoveguyy is offline Cadillac Owners Connoisseur
    Automobile(s): 03 STS
    Join Date
    Aug 2007
    mpls mn

    Re: Passive Strut Mystery

    krashed, i saw a link to a thread you commented on awhile back. you said to take the solenoid off a bad shock and tie it up inside the wheelwell area to keep the computer happy. i assume that means you than put in a passive strut? a resistor works on my 96sts. an earlier car needs the solenoid or coil to make the computer happy?

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