Check Engine Light on 1999 Toyota Camry

Check Engine Light The code is P0401 and P0402. We have replaced the carbon canister, MAP, Egr Valve, Egr Module (so... f_athens, 1999 Toyota Camry, 2.2L 4 cylinder, White, GA, June 26, 2009, 14:42 The code is P0401 and P0402. We have replaced the carbon canister, MAP, Egr Valve, Egr Module (solenoid) and one other part I don't remember the name of. Now the Check Engine light is on and both codes are coming up. My Mechanic which has be graciously helping me out is now ready to throw in the towel Help...

by in White, GA on July 08, 2009
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2 answers 1 comment
ANSWER by , July 08, 2009
Has your mechanic checked the basic EGR operation? Is the system allowing EGR flow into the engine? Did you pass on the articles that I posted in your previous question? I would have your mechanic read the articles, they should help to answer any questions they have about these diagnostic trouble codes, as well as how to diagnose the problems. http://repairpal.com/OBD-Code-P0401-Toyota http://repairpal.com/OBD-Code-P0402-Toyota
COMMENT by , July 08, 2009
I forgot to mention this is a Japanese built Camry..therefore some of the comments and instructions doesn't seem to apply. There has been enough differences in parts that I even had to start pointing out to parts store even though I've told them vin # begans with a J.
ANSWER by , July 08, 2009
The vacuum switching valve frequently fails. You test it for resistance and test it to see that it pases a vacuum when energized but they fail intermittently when driving. If this car has a vacuum modulator test the function of that the tests are pretty straight forward if you don't have the tests I will forward them to you. Check that the engine runs rough when full vacuum is applied to the EGR valve at idle but they are not as prone to passages plugging up as Hondas and Acuras and Mazda are.