hey guys, i have a '90 sedan deville with the 4.5L. My ABS started acting up and it would activate prematurely and it got to the point where it would turn on without pressing the brakes. I get an engine code of E40 which is "Open Power Steering Pressure Switch Signal." I'm pretty sure the brakes run off the PS pump and i think its a problem with the PS system which is causing the ABS issue. I have the Tevas MKII brake system. Any ideas of where to start to fix this?

any info is appreciated.

any suggestions?

I think that power steerng switch problem is fairly common. I have never looked at mine too close but it is supposed to be an electric switch on the steering rack. People have posted on here about their fixes, sounds simple and inexpensive.

cool, thanks i'll look into it a little more.

Brakes and PS do not interact hydraulically - they are separate systems so you have separate problems. Usually the only way ABS "self activates" is with traction control - which I'm pretty sure you don't have in a 93. If I understand the design correctly, the ABS does not apply hydraulic pressure to the brake system, it only relieves it, so unless you are pressing the pedal there should be no way for your brakes to activate, unless you mean the ABS just randomly cycles. I would suspect one or more wheel speed sensors. They are generally the most common ABS culprit.

ok, thanks for the info. At first without giving the brake pedal much pressure the abs would activate making it difficult to stop, then it got worse and to the point where the abs motor would run while not even pressing the pedal. i suspected wheel sensors at first but was unsure how to diagnose to which one(s) are causing the problem.

I didn't have ABS on mine so I don't know if it sets OBD codes. A factory service manual would have the diagnostic procedures. eBay or www.helminc.com are sources.

http://www.cadillacforums.com/forums/cadillac-tech-tips/55172-how-pull-codes-got-codes-warning.html

alright, its not throwing any codes, but i'll probably pick up a FSM soon and go from there. Thanks.

There may be a seperate diagnostic procedure for ABS. I know when I was having airbag problems there were two ALDL pins that when shorted caused the airbag light to flash a code sequence. Maybe ABS is similar?

does anyone have the GM part # for the power steering press. switch?

whens the last time you replaced the break pads cause i know my break light would come on when but break pads wer getting perty thin