Cause of EGR no flow code,p0401, when egr is still good? on 1995 Toyota Tercel

Egr "no flow detected", code p0401. EGR is still good! What is it? Heard- bad speed sensor, will set EGR "no flow" code?

by in Martinez, CA on June 07, 2010
1 answer 1 comment
ANSWER by on June 08, 2010
here is an article I wrote on Toyota PO401 code inspections. I would go through this article step by step. First thing to do is to raise the valve with a vacuum pump and the engine should die IMMEDIATELY, if not the system HAS to be cleaned out, I do Emissions work in CA and so I do this type of Diagnosis and repair every week. Trust me, make sure those EGR Passages are squeaky clean, then go from there, Good luck and ask more questions if needed.
COMMENT by on October 08, 2010
Was wondering if you could comment further on exactly what parts should be cleaned?? I have the same issue on the exact same car and have cleaned the EGR valve, cleaned the steel tubing from the EGR valve to the intake manifold, inspected and tested the VSV, and inspected and tested the Vacuum Modulator. I have tested the function of the EGR system by manually actuating the EGR and the engine gradually reduces RPM. I have also tested the system by unplugging the VSV cable and observed the EGR valve actuate under increasing engine load conditions. The only other thing I can think of is that the sensor that's reporting the P0401 code is faulting. Can you explain what that sensor is and how to test it?? Or perhaps suggest other places to inspect, test or clean?? Thanks.

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