Hi I have a 2001 Dodge Ram 1500 V8 5.9L. Several years ago I dual exhausted the truck and have been getting an engine light for the last couple of months. Took the truck to Auto Zone and their code reader was giving them a cautylist reading. So what I was told is that it may either be the sensors or the converter. I have 2 converters on the exhaust with only 1 set of sensors and they are located on the Cat coming off the engine. Went to O'Reilly Auto parts this morning and they looked up prices and according to their computer system, the truck should have 2 upstream sensors 1 downstream. So I'm trying to figure out where the 2nd upstream sensor would go since the converter they are reading only has 2 spots for the sensors. Thanks

 

California emissions trucks had four sensors. Federal emission had two. Cat Efficiency codes are not unusual with aftermarket cats.... I would test pressures on the exhaust, and see what ya get. If you have over 2 psi pressure at idle before the cat, replace it. If not, just do the non-fouler trick on the rear O2. (DIY in FAQ section.)