As Adrian infomed me in an earlier posting the booster pump on my car needed to be replaced after an incident where it didnt shut off..$600 bummer.

The pump was totally replaced and the brakes work great now..but I may have a related problem, not really sure. My mechanic said the brake light is still on...when he put the hammer on the car...the code said it was a latitudinal or longitudinal switch...I cannot remember.

He thought it might be related to the car sitting for awhile and thought the switch might fix itself with a little drivng. Since the new switch is $1300..I'm temped to drive the car for awhile to experiment...any thoughts?

Anyone know about this problem or can tell me what such a switch is for.

 

Wow! Are you sure the decimal place isn't in the wrong spot on the price of that switch? I hope that doesn't die on me.
The switches you're talking about, if I'm not mistaken, are used by the PDAS system to provide traction control. The lateral and longitudinal sensors (actually, I believe they're accelerometers) monitor the forces acting upon the car and attempt to keep it from spinning or otherwise going out of control. Adrian's book has a whole section on this system (pp. 210-225). The real explanation is much more in-depth, but basically that's the gist of it. One good thing is that the car is perfectly drivable even if the PDAS fails due to a busted sensor, since the ABS and other systems are unaffected. However, the handling characteristics will certainly be affected, and you'd lose the traction control of the PDAS. Come to think of it, I'm not really sure how having only one sensor would affect drivability, as I would think that would make for some strange operation. But I'm sure someone more knowledgable than me will chime in.
Brian

 

This issue has come up on various posts before. If you do a search for "accelerometer" you will be able to find them.

Before replacing anything though, it may be a good idea to try and clean the accelerometers. They are on the transmission tunnel, towards the front, on the right hand side, behind a cover of roughly 10x8 cm (I'm away from my car, the measurements may be off, but it is the only cover on the side of the transmission tunnel anyway).

They tend to attract metal particles and get stuck. I haven't tried personally, but you should be able to clean them back to life. Hope this helps.

 

Some clean them with compressed air, but be very, very, very careful. I seem to remember someone cleaning their accelerometers with compressed air and breaking them in the process. Ouch. There should be a thread about that around here somewhere...
Brian

 

I was told these are sealed units...looking more like relays than anything else. Is it the contacts that get dirty or the inside of the unit. Any idea how do you clean them?

Are they located around the gear shift...but inside the car?

 

See Jens's thread about potential pitfalls:
https://rennlist.com/forums/showthre...accelerometers

 

I'm driving the car now...the alarm goes off at 35mph and will stay on until the car is restarted. What is most confusing is there was no indication of a problem until the switch went out that caused my brake booster pump to die.

once the mechanic fixed the pump...he said he was getting an alarm on the ABS. I would love to know if one was directly related to the other.