Check Engine Light & Other lights on 2002 Pontiac Bonneville

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I have a 2002 Pontiac bonnevile SLE and My check engine light is on for a P1404 code. One of the pintle minimum position low limit values for the EGR pintle should be reading no lower than 0.7 and mine is reading 0.2. So it is failing the pintle minimum position value when the EGR is learning its position. In addition to this I replaced the EGR value with two different ones from Auto Zone then I also finally replaced it with an OEM EGR and still got the same EGR code.
I am not sure if it is the egr but it seem that when i drive for a long time I can hear the egr pintle rapidly opening and closing when I am at idle(but since it stops when I look under the hood it maybe something else).

Other issues that may be related are:

I think I have an intake manifold leak because I am loosing coolant and see wetness around that area. I also have a brake light, air bag light, trac off light, and anti-brake light all on at the same time. My oil gage is all the way to the right.

I am thinking that all these things are connected in some way because when I pulled the EGR valve off I see no blockage and I changed so many valves I dont know how all of them can be bad. I am thinking that maybe my PCM is bad and I might not be getting the right voltage to the various sensors and therefore it is making all of the lights come on giving false signals. I had the brakes checked out and they are fine so I dont understand why the lights would come on (monro muffuler checked them out).

What do you think could be the problem with the check engine light coming on and how do you change the PCM if it is bad (where is it located)?
(1) Answer
(4) Comments
First off I don't think all of these issues are related. For the EGR fault - try checking the EGR position sensor signal wire form the valve to the pcm - it could be open. Your air bag light is on because of a fault in the air bag system. Codes are set in the air bag module much the same as the pcm sets codes for the engine. The brake, abs, and trac off lights could be tied together. An abs fault can cause all three of those lights to come on and codes will be stored in the abs control module. As far as service information you can try the AutoZone website - Or for more complete information, at a cost, try - they have a DIY section.
The reference voltage is correct and the signal voltage should be OK. Did you check the signal voltage at the EGR valve or the pcm? You will need to check it at the pcm and it should be the same as at the valve.
The pcm is located in the air cleaner housing near the air filter. Try throughly checking the wiring from the egr valve to the pcm. If the signal wire is open or grounded that could cause your code to set.
Thanks for the help Russ.
I checked the signal voltage for the egr and it is reading about 1 volt and the ref voltage is about 5 volts. should i reset the engine light and then check this voltage? is the signal voltage within proper range?
I only checked it at the EGR valve. I am not even sure where the PCM is located except for the connector you plug the OBD2 into.