c1780 loss of steering signal

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Cadillac Seville / Cadillac Eldorado Forum Discussion, c1780 loss of steering signal in Past Cadillac Vehicle Discussion; just posting as a reference for future searches, as when I searched I found very few resources. so I bought ...
  1. #1
    pimpincaddystyle is offline Awaiting Email Confirmation
    Join Date
    May 2004

    c1780 loss of steering signal

    just posting as a reference for future searches, as when I searched I found very few resources.

    so I bought my 1998 sts with the code present and I replaced the steering wheel position sensor just because im an idiot and I didn't troubleshoot it. wasted 200 dollars. I could not find the SWPS on any schematic, alldata and Mitchell, not under abs, steering, or suspension diagrams.. wtf..

    so the SWPS signal is received by the EBTCM and converted into a PWM signal which is sent to the RSS module. everything I read had mentioned the gray wire being the wire that sends that signal. so I focused on that.. found that I did have a PWM signal at the RSS module so I thought the module was bad... but I then I realized on the suspension schematic, there were two wires for the PWM between the EBTCM and RSS. checked the other wire(white) and of course it was open.. wtf so easy

    looking at the EBTCM connector while its plugged in, its the upper right most wire (white) that was open.. the gray wire is right below that. I ran a jumper wire to save the trouble of pulling everything apart.

    the warning is now off and I cant believe how much better the car handles. it really does make a difference..
    I read that the RSS will still operate but just ignore the SWPS signal.. but it really likes all its inputs..

    hope this helps someone ..


    on that note I have my old one if anyone needs one...

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  3. #2
    ETC George is offline Cadillac Owners Member
    Automobile(s): '98 ETC that I love dearly
    Join Date
    Feb 2006

    Re: c1780 loss of steering signal

    Hello, I know it's been 10 years since your post but I'm having the same problem on my '98 ETC and wanted to THANK YOU for your input in the Caddie Forum. I have the advantage of owning an oscilloscope and I've checked the inputs to the RSS module. The SWP input to the RSS shows a pulse but when rotating the Steering Wheel the pulse width never changes.

    My dealer assured me the SWPS was operating perfectly so while troubleshooting, I feel like I'm banging my head against the engine block !!

    It sure would be nice if GM would cough up the waveforms for these signals and all other as well !!

    ETC George


    Sorry, I meant 1 year, not 10 years.

  4. #3
    MoistCabbage's Avatar
    MoistCabbage is offline Cadillac Owners 10000+ Posts
    Automobile(s): 2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
    Join Date
    Sep 2010
    East Boston MA.
    Quote Originally Posted by ETC George
    It sure would be nice if GM would cough up the waveforms for these signals and all other as well !!
    I highly doubt they have them, and there would be no need. No shop tests automotive sensors with an oscilloscope.

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