2005 Sienna- firing order/ #1 cylinder location

I have a 2005 sienna XLE V-6 3.3 L, check engine light, SCV light and TRAC light all on at same time. scan says P0051 HO2S Heater Control Circuit Low ( Bank 2, Sensor 1 ). I gather that is one of the oxygen sensors before the converter. My question is what side of engine is cylinder number one on, is bank 2 opposite side on number one cylinder or same side, would that be closest to front of van or closest to fire wall ? I seem to get conflicting info when I try to research it. I don't want to buy the wrong sensor as I see there not cheap. any pics would be great also. thanks...

http://workshop-manuals.com/toyota/sienna_awd/v6-3.3l_(3mz-fe)/engine_cooling_and_exhaust/engine/tune-up_and_engine_performance_checks/firing_order/component_information/specifications/

#1 is closest to firewall on passenger side

Ok, thanks Brian R, appreciate the info, couldn't even seem to find it in my chilton manal

ok, I ordered a new sensor online from autopartswarehouse. It came yesterday, I installed it, started it up and cleared the codes, everything is fine no warning lights are on anymore. drove a couple places across town and driving home all the warning lights came on again. frustrating. Not sure if its because the part is a cheaper after market or if there is some other problem with the vehicle. Any ideas ? Thanks.

after installing the sensor yesterday and driving it last night I never checked I just assumed it was the same code and the cheap sensor quit already. So I went and checked, its a different code. P0156 o2 Circuit ( Bank 2, Sensor 2 ) stored twice. My original post was P0051 HO2S Heat Control Circuit Low ( Bank 2, Sensor 1 ). that didn't show up before,why do you think replacing the first sensor caused this one to to have trouble code to now and didn't say that before ?, is there some other problem maybe ? How hard is it to get at this one to replace ?

Sensor #2 seems to be always more difficult to remove since it is more under the vehicle and thus more covered by road spray (salt). Many times, it takes a torch to heat the fasteners to get them to move. I don't use a torch in my garage for fire hazard, so I always take that job or any job needing a torch to Toyota or a trusted mechanic.

Not for nothing, I would cancel the code from memory (pull the ECM fuse for a min or use a code reader) and see if the code returns. I have had many Sensor 2 codes disappear and stay gone for a long time if I delete them from the ECM memory.

ok, I replaced the down stream one finally. cleared the code, drove it a few places around town and on my way home the warning lights came on again. the code is the same P0156 ( twice its stored ) o2 circuit ( Bank 2, Sensor 2 ). now whats the problem ?