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Replaced O2 (oxygen) Sensor Today - '2000 Ls400 - Obdii P0135


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2000 LS400 Platinum 107k miles.

The "Engine" light has been lit for several months on one of my kids' cars, so I finally broke down and bought a nice code reader.

Never needed one to work on my 2 Corvettes ('71/88), but I was dragged kicking and screaming into the 21st century I guess.

P0135. Oxygen (O2) Sensor Heater Circuit Malfunction (Bank 1, Sensor 1).


This code refers to the Upstream (before the catalyst) oxygen sensor on the Driver's side.

The sensor cost about $125 at the local parts store.

Started by jacking up the car with a floor jack and placing jack stands in the appropriate places. Removed the wheel/tire. Opened a beer (not required). Removed the rubber splash shield that covers the underside of the engine compartment. Actually, I removed the bolts/nuts on the driver's side half of the splash shield, and it hung-down enough to gain access. Located the sensor, which is nicely tucked away above the power steering lines. Disconnected the sensor plug from the wiring harness. Used a 22mm combo wrench (open end) to carefully break-free and then remove the sensor from the exhaust pipe. The exhaust manifold heat shield looks as if it's going to be in the way, and it is to some degree, but not enough to keep you from getting the wrench on the sensor. Careful not to damage the power steering lines while you're trying to break the sensor free. You can only get about a 1/4 turn before having to remove the wrench and flip it over to get the next 1/4 turn. Once it's loose you can easily remove it the last few turns by hand.

Installation is the reverse, remembering to apply the conductive anti-seize stuff to the threads of the new sensor BEFORE you screw it into the exhaust pipe. Also, do not attach the sensor plug to the wiring harness until AFTER the sensor is installed or the wire will become twisted.

That's it. No more codes or ENGINE light. Took about an hour from the time she pulled it into the garage.

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  • 1 year later...

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.

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first rule in auto ID...... set in the drivers seat, and from that position, determine LEFT & RIGHT.

now what sensor are you going to replace???

Hint-- (same one he did)

there will be a pop quiz tomorrow......

just having a little fun.... when you get under the car, you will see 2 cat/conv's with 4 O2's , the 2 closest to the radiator are what we call PRE, meaning in front of (before). the 2 closest to the trunk are what we call post, meaning after

good luck on yours, and welcome to the club

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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.


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...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.


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.

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