: Self leveling suspension noise?

05-07-06, 12:32 PM
2005 STS V6 with 1300mi.
There is a noise (hissing sound) coming from the rear wheel well area. It sounds identical from either rear wheel well. It occurs when the car is parked, locked and the driver or front passenger outside door handle is pulled. It occurs whether you have the remote with you or not (that is, it occurs whether the door unlock mechanism is activated or not). One simply has to pull on either front door handle. Then, if you listen at either rear wheel well area, you will hear a 2 to 3 second hissing sound. It always seems to be of approximately the same 2 to 3 second duration. If it has just occurred and you pull the handle immediately again it will not occur. However, if you wait approximately 30 seconds and pull the handle then it will occur again. This is a seemingly random occurrence. It does not happen all the time. Again, it happens whether the door unlocks or not. It is definitely not the unlock mechanism.
We also have a 2005 STS V8 and it has never happened on that car.
I was at our local Cadillac dealership and of course it would not happen! They were stumped. None of the 10 new STSs in their lot did this (we checked). They want to bring the car in and analyze/ keep it till they can make it happen. Seems to be in the self leveling mechanism- best guess.

Does this mechanism operate to correct the leveling when the car is not turned on?
Has anyone experienced the same situation? It seems that someone ought to know enough about the self leveling system to know if this is normal or not.
If not normal then some reasonable explanation of causes/ corrections should be known.

05-07-06, 01:20 PM
Addendum to the above:
The sound, upon further inspection (which means that I got on the ground behind and beside the car), appears to be coming from under the car somewhere from midcar to the rear wheel area. It is heard well form either side and sounds like a brief running of an electrical pump of sorts. Why would any thing like this be tied into the function of the front door handles?

05-07-06, 02:44 PM
I got out the Rhino Ramps and jack stands. I backed the STS up the ramps (carefully, as I know of a Corvette owner who has shot his Rhino Ramps under his Corvette while backing up on the ramps- not a pretty picture). The sound is/appears to be coming from the right fuel tank. I suppose it is from a fuel pump within the tank.
I have had cars that ran the fuel pump for a few seconds when the ignition was switched to on in order to build fuel pressure before the car was started. It sounds much like that brief fuel pump run.
Why would this be connected to the door handles? A short? Computer malfunction?
I will have more info to discuss with the dealer now.
Unless there is some other pump/mechanism above the right fuel tank, then the sound must be from within the right fuel tank.
Anyone with a similar concern?
Will keep you posted when I find the answer.


05-07-06, 10:57 PM
There are a lot of electrical events that occur when you pull the handle of the car if you have the keybob in your possession. Some of the items are controllable in the configuration panel such as whether the seats will move to the designated position for the key bob, whether all the doors will unlock or only the driver door, etc, I image that whatever that motor is that you hear, it is not a computer glitch of the handel but, as you said, a fuel pump, or leveler.

05-08-06, 08:15 AM
You don;t have to have the FOB in your possision for most of the systems to make noise. Pull the handle without the FOB and the doors locked and the car makes the same noises, turns on the exterior lights and starts the nav DVD spinning. All normal as far as I can tell.

05-13-06, 06:25 AM
Sounds like someone may have programmed the car to prime the fuel pressure when you get in the car. I would suspect it's normal, although I haven't monitored for this condition.
If I remember I'll see if I hear it on any STSs that I work on.
I wouldn't worry too much about it. With the passive entry system, all kinds of things can happen when you pull that door handle that you, or I, don't know about.

05-13-06, 05:51 PM
Thanks ewill3rd!
I take it into the dealer on Tuesday. Will keep you posted on results. The service director has discussed this with GM and so far no answers. Will see what comes up at the visit Tuesday.


05-18-06, 06:55 PM
Had the car into the dealer for evaluation Tuesday. While it was there, they took delivery of a new STS V6 and guess what- it does the same thing! They checked the other new V6s in their lot and neither did it until they realized that both of those car's batteries were dead. When their batteries were renewed they did it too! However no V8 did it. So.... it seems that the fuel pump runs for a few seconds to prime the fuel system on the V6 STS when the engine is off and any of the following occurs:
Either front door handle is pulled with car locked or unlocked. (with or without key fob in vincinity)
Trunk is opened. (closed?)
Hood is closed. (opened?)
Front door is closed after being left open for 30sec. or so.
Key fob lock or unlock is pressed.
Trunk unlock is pressed on the keyfob.
Front door is unlocked with key without pulling the handle.

Still seems mighty strange. Why is it set up this way?
Someone must know the answer.
The guys that prep all the STSs at the dealership said: Yes, all the V6s do that but none of the V8s. They have noticed it when they prep the vehicles.

05-18-06, 08:20 PM
If I had to guess, I'd say that it has to do with ECM initialization.
When the message from the handle wakes up the equipment to open the door, it probably initializes the ECM. Most ECM/PCM/VCM setups are designed to run the pump at key on. Key on used to be a relay or fed off the ignition switch, nowadays the "power mode master" gets a key on signal and sends out a message on the communication bus to wake up the modules.
I'd say you are just getting your fuel pump prime when the wake up signal goes out rather than with the ignition on. Especially with the easy key setup.

Not sure why it would be different than the V8. My guess would be that they are using the XLR ECM. Of course both have easy key.... hmmm.
Well that's my theory anyway.
Not sure why it's different.

05-19-06, 05:15 PM
Thanks ewill3rd.
Surely some engineer from GM must know the answer as to why they did this but we might never know.
Anyway, I certainly am enjoying the car.
Thanks for your time and thoughts.


05-19-06, 09:12 PM
If they ever come up with a class I haven't taken, I'll ask an instructor.

Actually I have a GM instructor at my disposal. If I remember I'll ask him to see if he can find out. I think he has some engineering phone numbers.
I know he has access to stuff that I don't.
I have some engineer's email addresses too, but they work on different carlines.
If I remember I'll ask someone.

05-20-06, 08:03 AM
Once again, thank you ewill3rd.
If I get any further explanation, I will inform you.
Much appreciated.

05-23-06, 07:38 AM
I posted this question on the GM tech forum so far no one has any information on this.
I still think it's a wake up of the ECM that is causing this to happen.

05-23-06, 06:53 PM
Thanks ewill3rd.
I hope we finally get an answer.