97 es300 cel = p0135

[triplethreattt]

Good afternoon...I have a 1997 ES300 (175K miles) and the CEL came on. The code is P0135, and after reviewing the procedures in the FSM, I see that the first check is on the ECM. I'm guessing (at this point) that the ECM is probably good. The second troubleshooting step tells me to check (and replace if bad) the Heated Oxygen Sensor (Bank 1 Sensor 2). This seems to me to be a greater chance of being the point of failure, so I've decided to head down that route first.

Has anyone replaced this sensor before? The book tells me to remove the driver's seat and the carpet. Is there another (read: EASIER) way around that? Does what sits under the carpet then go through the floor into the exhaust?

I'm fairly handy...but never worked on an O2 sensor before, and would like to have a better idea of what I'm getting myself into before I get started. Any assistance would be appreciated!!! Thanks!

It also appears that Autozone may or may not be able to help me properly figure out which sensor that I'm going to need. Any advice there would be helpful as well.

[triplethreattt]

OK...here's what I have found out.

Bank 1 is on the side of the engine closest to the firewall. Bank 2 is the one closest to the radiator.

Each Bank has 2 sensors, 1 before the cat. converter, and 1 after. The sensor BEFORE the CAT is an Air/Fuel Sensor, and the one AFTER the CAT is an O2 sensor.

Functionally they are the same thing, with subtle differences in operating ranges as far as what levels they are sensing.

Trying to get the part number is going to be the hardest part. Will post any updates!

[danielsatur]

Don't forget a heated H02 sensor has a fuse.
The down stream HO2 sensor just tells the ecu, if the catalytic converter is working, I would have no problem putting a used one in for the replacement.
The most important HO2 sensors are upstream for the air/fuel mix.
Consider buying two new H02 sensors for banks 1 & 2 upstream, and put the used ones down stream.

[triplethreattt]

any idea where this fuse is? it would be pretty nice if the problem was simply a blown fuse, although with 175K miles, I won't hold my breath.

[Brian R.]

Originally Posted by danielsatur

Don't forget a heated H02 sensor has a fuse.
The down stream HO2 sensor just tells the ecu, if the catalytic converter is working, I would have no problem putting a used one in for the replacement.
The most important HO2 sensors are upstream for the air/fuel mix.
Consider buying two new H02 sensors for banks 1 & 2 upstream, and put the used ones down stream.

Just in case anyone is reading this thread, you can't use the upstream (#1) sensors downstream (#2 sensor position) of the catalytic converters. They are totally different sensors and must be replaced with an identical sensor in all cases.