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Old 01-26-2014, 07:27 PM
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smj999smj smj999smj is offline
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2006 Pathfinder
2003 Frontier King Cab
2003 Frontier KC SVE 4x4
 
Join Date: Jun 2012
Location: Prospect, VA
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The frequency of the rich-lean cycling of the front and rear O2 sensors should be at an approximate ratio of 2:1 (front to rear) with the engine warmed up and vehicle driving at highways speeds if the catalytic converter is working efficiently. A 1:1 ratio would indicate the converter is not working efficiently. Some will put an O2 sensor spacer on the rear O2 sensor to "trick" the ECM and cause the code to not set. The spacer pulls the rear sensor partially out of the exhaust stream, so it still produces a reading, albeit an inaccurate one. If you have strict emission testing in your state, they will fail if they see the extender on the sensor.
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