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Old 05-12-2019, 11:43 AM   #10
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 45,201
 

2003 L-Series 3.0L Sedan
Default Re: p0420 AND p0430 - 2007 Saturn Vue 3.5L V6 AWD

OBD I, '91-'95 vehicles were the first generation of automatic on-board emissions self tests. Some states like N.Y. required exhaust gas sniffers while the vehicle was placed on rollers to allow various speeds. The inspector sat in the car watching a rudimentary GPS like map telling him what speed was needed at certain points of a regulated test drive. Speed and exhaust output were correlated for the emissions tests. Approximately 30 minutes per emissions inspection but this included setup on the rollers and coordinating from the beginning of the test drive until the end. I was informed that each 30 minute test equated to a maximum of 16 inspections a day for an 8 hr day. Probably less vehicles per day as one service bay was dedicated to emissions inspections. Stations lost money on this venture and made up lost revenue with repairs. When OBD II replaced OBD I, exhaust sniffing and rollers went away. OBD II does its own emissions self tests every time the engine is started and vehicle driven, monitored the entire time a vehicle is running.

The exhaust manifold mounted O2 sensors monitors engine emissions and feeds signals back to the engine computer for instantaneous adjustment of air/fuel mixtures for the lowest emissions during engine running. The O2 sensors mounted after the catcons monitor catcon efficiency. The front and rear sensors on one side of V6 engine are compared and if outputs are the same the catcon is worn and requires replacement. Normal catcon efficiency is a steady value between 0.4-0.8. Precat sensors show varying values as sensor frequency occurs a few times per second with lambda sensors operating differently from original sensors. Lambda sensors output around 1v and fluctuate plus or minus a few tenths of a volt while the downstream sensors output a steady value.

Sensor-1 are upstream (of the catcon) sensors. Sensor-2 are downstream (of the catcons) sensors.
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