Service suspension system speed limited to 90mph
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  • 1 Post By rmay
Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Service suspension system speed limited to 90mph in Past Cadillac Vehicle Discussion; Hi everyone! I recently converted my 2001 Cadillac Deville DTS rear air suspension to a non air suspension using a ...
  1. #1
    rmay is offline Cadillac Owners Member
    Automobile(s): 2001 Cadillac Deville DTS
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    Service suspension system speed limited to 90mph

    Hi everyone!
    I recently converted my 2001 Cadillac Deville DTS rear air suspension to a non air suspension using a kit by Monroe(90007) The car now rides fantastic. Better than it has in years. I looked long and hard to find affordable stock replacements.. (everyone laugh) But, I decided to go with the Monroe's instead because of the cost factor... Anyways.. Like the title says, every time I start the car or turn on the ignition, the dash reads "service suspension system" and "speed limited to 90". Just a quick push of the reset button makes the warnings disappear but they come back on every time I restart the vehicle. I have done a lot of searches on line and have not yet found an answer of how to clear the messages, or if it's even possible.

    I pulled the fuse to the compressor that inflates the rear bags... One thing I did notice is that my car's rear now sits a good 1 inch or so higher than it previously sat. Don't know if this could cause the warning error? Any help would be greatly appreciated!!

    My apologies if this has been asked a hundred times. I pulled the codes if that helps. Here is what I got. C0589 - C0594 - C0657

    Ryan
    CadillacLuke24 likes this.

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  3. #2
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Service suspension system speed limited to 90mph

    Not only does your car use rear level control (not 'suspension control' - rear level control to compensate for extra weight in the trunk or rear seat), it also uses electronically controlled electrical shock absorbers for suspension damping control. That missing electrical connection is what is setting the suspension messages because the non-functional damping makes the car dangerous to drive under aggressive handling conditions and speeds.

    Either restore the rear suspension control to the proper F45 control system or jury-rig a 4.7 KOhm 5 Watt resistor across the body wiring harness connector for each shock. Insulate well. Remember - the front struts are still active, the rear shocks are not, so some handling aspects might be a bit weird.

    A DTS (performance car) with proper active suspension and ride height should have a very slight forward "rake" when viewed from the side on a level surface.

  4. #3
    JimD is offline Cadillac Owners Connoisseur
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    Re: Service suspension system speed limited to 90mph

    Quote Originally Posted by Submariner409 View Post
    ....Either restore the rear suspension control to the proper F45 control system or jury-rig a 4.7 KOhm 5 Watt resistor across the body wiring harness connector for each shock.
    Just a minor correction.
    A 4.7K Ohm 1/2 Watt resistor is a (usually) available consumer item; Radio Shack item 271-1124. Anyone feeling adventurous might get lucky and discover a 4.7K Ohm 1/4 Watt serves fine and 1/4 Watt resistor values are as common as dirt anywhere that sells discrete components.

    It's all in the math and the iron-clad energy dissipation engineering standards.

  5. #4
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Service suspension system speed limited to 90mph

    I only went with the 5 watt unit due to size and lead ("leed") gauge.

    What is the current draw of the original suspension control signal (depending on maneuvering severity) of each strut and shock solenoid in the F45 system ?? Seems like the solenoids themselves would dissipate a bit of heat in a normal setup.

    Energy dissipation has nothing to do with a non-electronic consumer plugging in a jury-rig to "fool" a sensor/solenoid control system - ease of installation does. While a 1/4 watt carbon resistor would probably work, the leads are almost as fine as hair - let Joe Juryrig fidget with that with the car up on a curb.

    Anyone want resistors ?? I have several thousand in various shoeboxes in the shop. Free. All sizes.

    (Yanked out of a box at random) Which physical size would you rather work with ???

  6. #5
    JimD is offline Cadillac Owners Connoisseur
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    Re: Service suspension system speed limited to 90mph

    The risk here is posting data that is of zero interest to 99+% of the readers and will put the remainder to sleep.

    Quote Originally Posted by Submariner409 View Post
    ....What is the current draw of the original suspension control signal (depending on maneuvering severity) of each strut and shock solenoid in the F45 system ??
    As closely as I could "guesstimate", the average TOTAL current draw for all four oscillation damper solenoids was 12 ma observed while driving on as many different road surfaces as I could locate during a 30 minute test drive. Divide 12 ma by 4 four solenoids and each solenoid demands an average 3 ma. Average is a key word here.

    An owner focused on getting a few more miles/months/years out of a 12+ year old car should probably learn to ignore the messages that result from installing non-OEM parts.

    Seems like the solenoids themselves would dissipate a bit of heat in a normal setup.
    Correct. The difference is the solenoid is mounted to a metal component (heat sink) and is slightly liquid cooled. A stand-in resistor is hanging in free air and 'should be' covered with insulation which would inhibit heat dissipation.

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