I have a 1999 silverado 2500 has a code p0401 which is low e.g.r. control. I have replaced tubes and valve. Am I correct that the pressure is controlled buy the mas air reading. Which controls the e.g.r. trigger for the m.i.l.l. lamp. Also my bank 2 long term fuel trim is not changing its at 0. So could this be a restriction in the cat? It was working after I changed it a few months ago. I have bought a altel meter and the graft shows it not oscillating. all the others are around 0 to 2 oscillation. By the way I have checked all the terminals for reference voltages and control except the map. which is tomorrow project.
On another problem have a c0205 code on abs anyone ever try to resolder the terminals in board? The meter says the ground terminals inside are not working. I kind of new there was a problem with it as could make abs lamp flicker if i really pushed on plug. In the warm summer air its on all the time in the winter its off and on.
The Autel I'm using is a MS906bt Any one use this tester???

 

Well tested the mass sensor with my fluke v-88 was working perfect through all the vacuum added. Every thing was working had the mil lamp still on for egr. Do not think the exhaust is heating up as have a vapor cloud. I do not have a temperature gun to tell. Any ideas?

 

well it is still setting mil lamp. I be leave the sound is when the egr valve opens. The light is instant. Almost like it is sucking up a piece of carbon or converter in the exhaust manifold. Before I put new tube on egr at the manifold ran a cable in it to make shure it was open. Is that even possible to happen?

 

the egr checks the flow using the map sensor... manifold absolute pressure...not maf...mass air flow. the pcm expects to see a change in the map sensor reading when the egr opens...ie drop in vacuum.
if you have any map codes...correct them first