The EGR System tends to get restricted or blocked with carbon after 100,000- 125,000 miles which will cause an emissions test failure for NOX. If the EGR system is equipped with an EGR temperature sensor it will trigger a Check Engine Light for improper EGR flow. The repair is to clean out the EGR passages and the EGR Temperature sensor. Our technicians tell this repair is pretty straight forward and takes about 1-1.5 hours. It is also wise to verify the EGR system components i.e. the Transducer, EGR Valve and VSV Solenoid at this time.Google+
Car Problem Reports
Toyota Land Cruiser Failed Emissions Test Due to Blocked EGR System
Toyota Land Cruiser Problem
Visitor, 1997 Toyota Land Cruiser
Can't find solution yet. Have replaced all three components with no improvement of PO401 check engine code. Passageways are clear. Problem appeared at 150k miles.