Toyota Repair: PO401 code, toyota camary, exhaust gas recirculation

Question
QUESTION: Ted.I have a 1998 Toyota camary Le 2.2L japan made. I bought the car in August 2011 it has 127,000 miles. I have been trying since September 2011 to get the check engine light to stay off for code PO401: (Exhaust gas recirculation flow insufficient)as reads on my OBDII. These are the repairs my mechanic and I have done so far. Replaced egr valve, modulator valve, vsv valve, Large intake manifold hose that was weather cracked and had hole. replaced most vacuum hoses for all components mentioned above and visually checked all others hoses to be sure no leaks. Have checked with a vacuum pump the above mentioned parts to make sure they are working. Have checked electrically the solenoid  and they are opening and shutting and all check out ok. We cleaned the egr  tube of carbon. today we took the throttle body apart to clean it and the very small ports were clogged.after thoroughly cleaning put everything back together. Drove about 6 mile to the house and light came back on with same code what else can I check?

ANSWER: Hello, it should also have an EGR gas temp sensor mounted to the bottom casting of the EGR valve, make sure the connections are good, if so you may want to try to replace this sensor.

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QUESTION: Will this gas temp sensor trigger the PO401 ¨exhaust gas recirculation flow insufficient¨ Can you tell me what flow insufficient means?
John

Answer
The egr flow is determined by the egr gas temperature, the sensor monitors the egr temperature and sends this information to the computer, if all requirements are met otherwise and the temp sensor does not send the correct feedback temperature to the computer due to not enough  exhaust gas flow or a defective sensor the computer turns the check engine light on and sets this code.