Chevy & GMC Vans

The Astro is throwing a O2 sensor code (I don't remember if it was 141 or 144 as I have been erasing it because it was driving my wife crazy). I've been busy working on other cars so I'm now getting back to the Astro and want to replace the sensor as soon as it throws the code again.
My confusion comes in when I'm looking in my Helms and it shows the 4 sensors as B1S1, B1S2, B1S3, and B2S1.
This seems backwards to me since I would consider the left side of the engine "Bank 1" and the right side of the engine "Bank 2", and there is only 1 sensor on the left side, and 3 on the right.
Another issue is, from what I can tell from the Helms is all four are heated, which seems strange.
Putting this with the fact that while at the parts store buying parts for another car, I had asked if he stocked the O2 sensors for the Astro. He said he carried "both", and that the van took 2 heated for in front of the Cat and 2 non-heated for behind the Cat. At the time I knew this was incorrect. I knew the layout of the sensors (3 in the "Y") and one down stream behind the Cat, but at the time didn't argue with him as I had my mind on the other car at the time.
I just figured that the 3 in the Y were heated, and the one downstream wasn't.

Now, can someone map out the O2 sensors for me, and confirm that all four are heated?

Rufus, it's my understanding that the 'bank' designation of the O2 sensors denotes their position in relationship to the catalytic converter; bank 1 sensors are upstream of the cat (between the engine and the cat), while bank 2 are downstream.
Like yourself, I always thought that the bank referred to the side of the engine, but I couldn't figure out how the designation would work if the engine was an inline.

Bank #1 Sensor 1 - Right front Exhaust Y-Pipe closest to Exhaust Manifold
Bank #1 Sensor 2 - Left front Exhaust Y-pipe
Bank #1 Sensor 3 - Right front Exhaust Y-Pipe closest to Catalytic Converter
Bank #2 Sensor 1 - Exhaust Pipe, between Catalytic Converter and Muffler

They are all heated, two of each type. From what I remember, one type has a rectangular connector, and the other a square type.

It says in the service manual Bank 1, Sensor 1 and Bank 2, Sensor 1 is used to control proper fuelling and emissions. The other two are to monitor Catalyst efficiency.

Check on your code again when it comes up. 141 Means the heater in Bank 1 Sensor 2 isnt getting the sensor warmed up in time. 144 means the voltage stays above 993 mV for more than 5 seconds on Bank 1 Sensor 3.

Let me know if you need any other info from the book.

Scott

SafariRob wrote:Rufus, it's my understanding that the 'bank' designation of the O2 sensors denotes their position in relationship to the catalytic converter; bank 1 sensors are upstream of the cat (between the engine and the cat), while bank 2 are downstream.
Like yourself, I always thought that the bank referred to the side of the engine, but I couldn't figure out how the designation would work if the engine was an inline.

Thanks Rob. This makes total sense after viewing Scott's reply.

sfeaver wrote:Bank #1 Sensor 1 - Right front Exhaust Y-Pipe closest to Exhaust Manifold
Bank #1 Sensor 2 - Left front Exhaust Y-pipe
Bank #1 Sensor 3 - Right front Exhaust Y-Pipe closest to Catalytic Converter
Bank #2 Sensor 1 - Exhaust Pipe, between Catalytic Converter and Muffler

They are all heated, two of each type. From what I remember, one type has a rectangular connector, and the other a square type.

It says in the service manual Bank 1, Sensor 1 and Bank 2, Sensor 1 is used to control proper fuelling and emissions. The other two are to monitor Catalyst efficiency.

Check on your code again when it comes up. 141 Means the heater in Bank 1 Sensor 2 isnt getting the sensor warmed up in time. 144 means the voltage stays above 993 mV for more than 5 seconds on Bank 1 Sensor 3.

Let me know if you need any other info from the book.

Scott

Thanks Scott. This makes a lot of sense.
I still find it goofy that they would go from right (1) to left (2), and then back to right (3) for the three sensors on bank 1, but hey, if that's the way they map it, so be it. (Just seems that they would go left to right in the count.)
If you don't mind sharing the info, what book are you reviewing? I have been through both volumes of my Helms, but couldn't find any mapping if which sensor was which. It has lots of technical info on each sensor, but no where does it tell you the location of each.

Thanks again.

I thought I already posted a reply, I guess it didnt go through.

Its from the factory service manual

Scott