Over the time the exhaust gas recirculation (EGR) system may become plugged with debris, the oxygen sensor may also be getting slow or 'lazy' around this time. When servicing or cleaning the EGR system, it is a good idea to replace the oxygen sensor because it works in tandem with the EGR system.Google+
Car Problem Reports
Toyota Tercel Replace Oxygen Sensor When Servicing EGR System
Toyota Tercel Problem
Visitor, 1995 Toyota Tercel, 82,000 mi
The check engine light came on after EGR servicing. After diagnosing the issue, found the O2 sensor was plugged.