Does anyone have any idea how to fix a P0401 code on a 99 toyota tacoma prerunner 2.7l?

 

Well find the problem or at least narrow it down.

Do you have the California Emissions package as things are different in 2000 between the 2

I can`t say for sure as I don`t know weather things changed from 99 to 2000.

This is why it is great to have the diagnostics section in the Factory Service Manual for your vehicle and at least a code reader.

To go step by step to troubleshoot this online would take hours.

 

Check the egr vacuum switching valve.

 

I had this problem, and corrected it by removing and cleaning the EGR temp sensor. Now, the 401 code pops up once per year, instead of once per week. Eventually, I'll replace the sensor.

 

I just looked up the prices and the vacuum switching valve is 60 dollars and the EGR temp sensor is 210 dollars. Why must the sensor be so high???