Whiteshark

...where would we be without the Internet. I think steviej's post was referring to a different engine altogether (perhaps transverse mounted and maybe cylinder 1 was located differently) - so my bad. Billy - you are clearly correct. Found another site that had a post in reply to someone asking for firing order and cylinder #, it stated "For the LS400 1UZ-FE V8 the firing order is 1-8-4-3-6-5-7-2, RH from the front 2-4-6-8, LH from the front 1-3-5-7. The RH/LH of the engine is facing forward, in other words, from the drivers seat looking forward". So (and please correct me if I'm wrong - don't want to screw up someone else's head) Sitting in drivers seat...my cylinder 1 (located in "bank 1") is up closest to the radiator and would be left hand (drivers side) and sensor 1 is "pre" - on the side of the catalytic converter closest to the radiator (as opposed to sensor 2, which is closest to the trunk). So I need "pre cat left" from that web site. Correct? P.S. - probably a smart move to just go ahead and replace bank 2 sensor 1 as well - I figure it will trip the check engine light fairly soon as well.

Thanks...but I'll tell you why it's confusing. Search on PO135 from steviej (author) and by all means not trying to call him out as being wrong (he is clearly a knowledgeable poster) - I find the following text... Bank 1 is the right hand three cylinders (RH) that are against the firewall, that information was correct. O2 sensor bank 1 sensor 1 is the one in the RH header/exhaust manifold assembly. Yet In this thread the "Driver side" is clearly indicated...but if I'm sitting in the drivers seat looking forward (as you suggest) - that's the left side. So which is it? Pre and Post Catalytic converter...so again it tells me there is an OS sensor before and after...but from what perspective. More importantly, is perspective of the web site that sells the parts based on some form of a "standard rule" as you say. Just a part # would solve all this, but I could not find one on this forum specifically for my car (99 LS400). Time to call Toyota I guess. kb

Question (below). I have the exact same thing (P0135 - which we all know is bank 1 sensor 1) - I have 1999 LS400 w/95K. From what I have read in various posts on this forum - it's the right hand side, between the engine and firewall, accessible either from top or underneath car. If also found people referring to www oygensensors com as the best place to buy them on-line. But as I got there and punch in my make, model, year - it comes up with four sensors. pre-cat right, pre-cat left, post-cat right or post-cat left? This topic suggests "Driver side", but of course if you are looking at the car from the rear that would be the left side, if looking from the front of the car it would be right side. I presume it's pre-cat right - but not 100% sure, hence I'm posting here. Any help appreciated.