Oxygen Sensors

[crsgmc]

1996 GMC K1500 5.0 engine

I have a quick question. Often times you hear people say that the 5.0 has three oxygen sensors. This is not accurate. The 1996 305 has four sensors. Bank 1, Bank 2, Post Cat, and a fourth one that is located in the Y of the Y pipe. I have the GM manual for a 98 which is very close to a 96 and it also shows five sensors as listed above. The Y sensor is listed as inactive. My truck has this sensor and it is wired into the system. What do they mean by inactive? Why is there a sensor if it is inactive? I am replacing the Y pipe when I ran into this. Thanks for any help.

[crsgmc]

The Y pipe and Catalytic converter that I purchased also contains a plug for one of the O2 sensors. There were not instructions with the part. Does this sensor activate when one of the other sensors goes bad? I would have to think that GM has it in the truck for a reason. No one knows anything about this sensor?

[Palf70Step]

I wish I could help you with ur question. Not sure, but normally all O2 sensors are their own thing, not a backup for another. Been a Long time since I had a truck with that configuration so I don't remember any specifics.

[ChevyTech]

On both bank 1 and 2, the sensor closest to the engine (exhaust port) is the sensor used to control the mixture. This is an active sensor. The other sensors are there to monitor catalyst efficiency but have nothing to do with the mixture or engine control.