I figured I would pass this on in the event someone else had the same problem - they could save a good deal of $$$. Here's the story, my CEL came on in my LX450 a couple months ago. I had the code scanned and it turned out to be P0401 " EGR Flow Insufficient ". I took the vehicle to the local Lexus dealer - who charged me a service charge merely to scan the code again. Further, they stated that the, EGR Vacuum Modulator, the Vacuum Switching Valve, and the EGR Gas Temp Sensor, were all bad. They stated that for parts and labor the total would be $800 plus tax. I payed the $89 service charge and took my vehicle home - $800 f*&^$ing dollars ! I found it very hard to believe that all three parts went bad simultaneously. I then checked the rubber vacuum hoses for leaks - there were none. I even opened up the EGR Vacuum Modulator and cleaned the little filter and reset the CEL - a day later it came back on. Then I checked on the price of the parts and it turns out the cheapest of the three was the EGR Vacuum Modulator - essentially a vacuum diaphram. It was also the easiest to replace - right on top of the engine. I called the local dealer for the price - $90, I then called Carson Toyota and got it for around $55 - much better. I received the part last week and installed it in less that 10 minutes. It's been a week now and no CEL ! So I save almost $750 - very nice indeed. Hopefully this will save someone with the same problem from forking over a chunk of hard earned cash. I can get you guys the P/N for the EGR Modulator if you need it.

 

I have a code 71 on my SC right now, "EGR system malfunction"...funny thing (well, actually not so funny) is that I replaced the damn modulator a little over a year ago. I wonder what the heck is wrong with it now? I guess I just have to clean out the valve and make sure the diaphram can move up and down and just replace the $2 gasket. Hopefully it's not that hard as I'm no mechanic...