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Hi,

I have a 2003 Serville STS and the are several faults that are displayed (Diagnostic Trouble Codes) The Codes t hat I'm concerned about are "Service Suspension System" "Service Stability System" and "Speed Limited to 90MPH"

Having attempted to clear the Codes and spending a considerable amount of money having the whole suspension system serviced and parts renewed where required. It transpires that the fault lies in the computer itself. I have been told that the vehicle requires a new computer as the old one can not have these codes removed.

My questions is two fold:-

1) Is there somewhere I can obtain a second hand computer?

2) Is there a means of by-passing the speed limiter?

3) Is there any other solutions that do not involve trying to reset the codes.

I am completely satisfied that the is nothing wrong with the suspension or stability systems.

I look forward to some advice and help.

Susan

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First, make sure the connector on the computer is OK. We've seen a few fail, and sometimes the pins get pushed back into the connector as it is being installed. I'd say you could get a new one from the scrap yard, but it must be the same make, model and probably year. Finally, my 1999 STS had this issue intermittently, but when the message was displayed my speeds were never actually limited.

You should be able to feel the suspension stiffen up slightly as you approach or exceed 70 mph or so, just to verify that the suspension is working as designed.

Never underestimate the amount of a persons greed.

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The computers very rarely go bad. When they do, it's something like jumper cables hooked up backwards and that blows a lot of things out, like the radio, nav system, and most or all of the modules (computers). Clumsy electrical work can pop one computer but that is really hard to do and it is rare, and what you see is a dead module, not persistent codes.

If you are seeing persistent codes, it's because the computer is seeing the codes persistently. There are a lot of ways that can happen, but JohnnyG's advice is excellent. Bad connectors is the most likely cause, if you are sure about the suspension components.

You can run the codes yourself. See the link in my signature block for instructions.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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If the shocks and struts were replaced with aftermarket parts, there needs to be a resistor added to the vehicle side of the strut/shock harness or the SERVICE RIDE CONTROL message will set.

OFF and INFO UP will put the system into diagnostic mode. ALL? will be displayed.

To operate the diagnostics, the following buttons are used:

  • ON/OFF = Yes
  • INFO RESET = No
  • INFO UP/DN is the toggle to between systems
  • To exit the diagnostics, repeatedly press the INFO RESET button or turn the ignition to OFF.

Any codes will be displayed on the DIC as CURRENT or HISTORY.

Post the codes and we should be able to pinpoint what is causing the SPEED LIMITED TO 90 message.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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I will try to get the connectors looked at.

However, as when I tried to get an answer previously (about six months ago) no one can tell me how the speed limiter can be by passed as it indeed limits the speed.

Please, please is the an answer to this simple question.

Thanks in anticipation

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I will try to get the connectors looked at.

However, as when I tried to get an answer previously (about six months ago) no one can tell me how the speed limiter can be by passed as it indeed limits the speed.

Please, please is the an answer to this simple question.

Thanks in anticipation

Susan,

As far as I know, as long as the suspension or stability messages are CURRENT... the speed limiter can not be bypassed.

That is a built in function of the programming.

When the suspension and stability issues are dealt with, the speed will no longer be limited to 90.

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It sounds like someone replaced your electronic shocks and struts with non-electronic shocks and struts. That disables RSS which stiffens the shocks under certain conditions, such as higher speeds. If the new parts are stiff enough for safety at high speeds, you can by-pass the connectors for the shocks and struts with resistors without a safety problem. The OBD codes from your car's computers will tell whether the problem is bad connectors on electronic shocks/struts or simply disconnected connectors.

If the codes show all four shocks and struts are disconnected as CURRENT codes, we can go from there.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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