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99 STS dead, then total strangeness


bigfoo

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This is a strange story.. and one that doesn't have an ending yet...

I woke up one day and the car was dead.. battery completely dead.. so I jump started it of course..

Then the weirdness happened.. the first thing i noticed was the sunroof didn't work any more.. ok no big deal right now the car stiill works.. so i drove it for a while and noticed the headlights were on and it was daytime.. ok i can deal with that; i turned the automatic headlight thing off and they went out.. so at a stoplight i decided what the hell, i'll check for some codes so i went to look at the codes and there was like 20 of them, most history but about at least 3-4 current ones which i haven't written down yet but I will later and post..

So, Woah, what in the world......... a few starts later i hit the sunroof button and it works again .. <?> then in a parking lot i was outside the car while it was idling and i hear this sound coming from the back like a small electric motor turning high rpms and it doesn't stop.. ok NOW what? Anyway after another week of driving suddenly the headlights work again (they come on at night and go off during the day)..ok now im stumped..

Another few days and it now says SERVICE SUSPENSION SYS on the DIC.. Ok, now I have to post a message on the forums and find out what in the world....

I'll reply to this with a complete list of the codes once I have time to write them all down.. they go by so fast :)

I did some tests like going 5-6 mph and slamming on the brakes and the car bounces back and forth about 3 times before settling.. I'm not sure that's the correct reaction from the suspension (i really never did that before heh)

And what the kicker is... it's just out of warranty now.. why couldn't this have happened a few months agooooooooooooooooooooooooooooo......... arggh :)

Thanks for reading!

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Sounds pretty simple to me. Something stuck on, like your suspension air compressor relay, draining the battery completely. It unstuck itself for a couple of days and the battery charged back up. The way the power management system works on the '99 started cutting off unneccesary stuff, like the sunroof. Now it appears to be sticking again since you can hear it, or some other control is causing it to run. Fix the current suspension codes and you should be back to normal.

Never underestimate the amount of a persons greed.

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i would clean all the stored codes up and drive it for a while to get new ones (no irony). this way you'll get thecodes which count... ;)

The saddest thing in life is wasted talent

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Ahh ok! Thanks guys! I thought I had ghosts in the computer or something. This morning the service suspension sys message dissappeared also. Is there a way to reset the whole computer and have it start all over? I tried unplugging the battery a long time ago to reset some settings but it kept the settings; I'm assuming it has some sort of nvram or flash that stores the info on ..

Maybe there's a little programmer or something i can buy to plug into the service port?

Thanks!

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I had similar problems on my 98 STS. The first abnormal thing I noticed was that the e-brake was not releasing which was leading my to think it was the electrical mechanism that releases it. Then, other strange problems began occurring like ABS lights, traction disabled, certain features not operating (like sunroof). I finally took it in and it ended up being a bad ignition switch which was not an expensive repair (luckily it was still under warranty). Apparently, the different modules were not getting the power they needed at startup which was causing the variety of problems. Once the switch was replaced, car was back to 100% again! Hope yours is something similar.

Max

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arrghh it's at it again...................... no more suspension messgaes, but now the headlights stay on again and the heater in the drivers seat doesn't work (and i just had that replaced several months ago).. hEH..

AT least it still runs :)

Any idea where the sensor is for the headllights and how to replace it and where to get one?

thanks

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OK... so where is the sensor for the headlights ? The night/day light sensor?

I guess i'll be checking bulbs :) Although nothing has been replaced for almost 6 months in terms of bulbs .. but you never know I guess :>

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bigfoo,

Read through the posts to the following thread (below) from this past March, which was started by "BOB W." Pay attention to my posts in the thread -- I discussed the process for removing/replacing the ambient light sensor in Seville models of your type. However, as was the situation with the old thread, I am uncertain of the exact symptoms that you are experiencing, so I am unsure if the sensor is actually the root cause of the problem.

Apparently, there never was any follow-up from "BOB W." explaining the outcome of his situation. I ultimately had referred him to a Cadillac dealership, and you may need to do the same thing.

http://caddyinfo.ipbhost.com/index.php?showtopic=1019

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Ahh thanks! But I'm confused.. in one sentence you say the grille pops in and out on 98+ sevilles, and then in another you say trying to pry it out on a 98+ seville will result in problems..

So, how do i get it out? :)

And i guess there is no way to test to see if it's the sensor or not ?

Is there a little thing i can buy that plugs into the data port and I can see sensor readings? I know the DIC won't show anything like that but there must be something else..

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bigfoo,

I don't understand the source of your confusion -- I thought I was fairly clear in my posts in the old thread. But just to clarify: the defroster grille on all '98+ Sevilles is NOT A SNAP-IN PART! The grille is held in place with screws underneath the upper trim panel for the instrument panel (i.e., the "top pad"), which must be removed first. All of this work is fairly easy, provided that you know what you are doing. Otherwise, it is a job best left to professionals.

A Tech 2 GM service tool ("scanner") can be used to communicate with the instrument panel module (IPM), which is a part of the HVAC control module. This module is the one that "reads" the ambient light sensor. The Tech 2 can be used to "display data" for all of the various electronic modules in the vehicle; when the Tech 2 displays the IPM data, the light sensor voltage ("counts") will be displayed. The sensor can be exposed to either bright light (from a flashlight, for example), or covered up to see if the voltage changes appropriately. The GM service manual describes appropriate "counts" values for light and dark conditions. This way, you could determine if the sensor is functioning properly without having to physically access the sensor.

There is diagnostic trouble code specifically for ambient light sensor problems, DTC B2419, which can become set in the IPM. Have you checked codes using the onboard diagnsotics? Were there any set in the IPM?

Overall, I have to say that unless you have access to a Tech 2, or are prepared to perform quite a bit of disassembly of the vehicle's interior in order to perform electrical circuit checks with a digitial multimeter, then I think it would be best for you to have this problem checked/repaired by a Cadillac dealership. In any case, if you are serious about doing your own work on this vehicle, get yourself a GM service manual. However, as I indicated in my post in the older thread, be advised that a printed manual may contain an error regarding the removal of the defroster grille.

Good luck! If possible, please post the outcome of your situation.

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