I found the front one easy to replace but struggled a bit more with the rear one. I did use the special tool to loosen the old sensors.

After trying and failing to release the plug from above I went underneath and took off the sensor. The wires twisted as I unscrewed it, but not too much. With the sensor released from the manifold, I kept it held in my right hand while I reached up with my left and pressed the clip on the plug. As soon as I heard the click, I yanked the sensor with my right hand and out the plug came!

 

You may like to check with ES forum. For CEL I note the error code and clear it once. If it does not come back then I forget about it.

My motto with vehicles is do the regular maintenance but never over do stuff. Many things can go wrong inadvertently.

Salim

 

X2. Don't fix what ain't broke.

On sensor two on sister's 1999 RX-300, I used Bosch universal w/ trick connector to avoid having to go inside and remove rear seat for her sensor #2 connector, the after cat. IE, I terminated the sensor wiring with extreme prejudice under the car. Its been in ~5+ years, no problem. The original had one of its fasteners sheared off (they have two bolt flange that the O2 sensor screws into). Tire monkey damage, I dunno? That left the sensor kinda exposed to ambient air and -might- have had something to do with the trouble code. BUT....I had bought the Bosch sensor, and the new one was darn sure going in. I lucked out and was able to remove stub of original fastener with Vice-Grip and rethread hole to fit the new Bosch (which had an 18 mm?) sensor that screwed into a stainless steel flange to duplicate the Toyota mount.

 

I had P1135 and tackled this myself. Thanks to all the DIY help here. I got the loaner tool from Autozone. Used an 18" breaker bar to break the sensor loose, then a ratchet got it out rest of the way with no real issues.

The connector was worst part. I had found another diy where someone chained 3 zip ties together onto the wire and pulled it out from pasenger side under hood. I could see the connector from the top, but my hands are too big to get down there. I could reach from the bottom easier, but still only with one hand. So I bulit my zip tie chain, pressed the button on the connector with my left hand and pulld on the other end of the zip tie chain from the passenger wheel well. That actually worked pretty well.

Good news is P1135 is gone now. Bad news is I still have P0330 and I am not sure I want to tackle that knock sensor job DIY.

 

When replacing it is a good Idea to check manifold for cracks around the threaded insert, I have seen many front manifolds with cracks present and they only get worse.

 

After reading as many posts as I could find, I tackled both A/F sensors (throwing both codes, plus a thermostat code that apparently can sympathetically trigger - - confirmed it was just the A/F sensors) . Some quick thoughts:
- Denso 234-9009 parts at Amazon
- Since you have to reach up under the car, ramps seem like they might be too high. I put jack stands under the frame that just barely still had tires on ground, and that worked well.
- Just follow the exhaust manifolds to the pipe flanges, and each sensor is found easily at that intersection.
- Used PB blaster and A/F socket and had no issues getting either sensor out (no rust South helps!). Used breaker bar underneath, but there was not enough space for bank one (could have gotten-by without the breaker bar)
- I use a small flat head screwdriver to wedge into the Lexus clips, and that works well in releasing if you rock the male/sensor side
- Took me about three slow/methodical hours start to finish to replace both.
- Avoided $600+ of labor charges quoted to fix
- Engine light is off, and just passed inspection in Houston area (and the RX300 lives to see another day)

 

Just a reminder ... so the information does not get buried way down ...

Dealing with sensors in the exhaust, make sure to work the threads.
Budge it and then re-tighten 1/2 way.
Undo 1/4 turn redo 1/8 turn.
Undo 1/2 turn redo 1/4 turn.
repeat 1/2 turn 1/4 turn till the sensor falls out.

Salim

 

Quick question - CEL/VSC/TRAC OFF lights, code read at AutoZone is p1155, so bank 2 sensor 1. The print out they gave me says probable cause: Open or short circuit condition, or AF Sensor heater relay fault, or Failed A/F ratio sensor.
I'm thinking that if the fault is with the relay itself, I would have gotten codes for the other sensors as well, not just p1155 for the bank 2 sensor 1. So in that case I should order the Denso replacement and change it out.
Is my logic sound?
If not, how can I determine if the relay itself is okay before I order the $95 sensor? (I don't have a mulit-meter or any diagnostic equipment.)

 

The relay should supply 12volts to the sensor to heat it up (and therefore get into closed loop operation quickly).

So if you have voltage going to the sensor then the relay is sound.

Also, you can reset the error code and if it stays gone for a while and comes back I'm fairly certain that the heating element in the sensor is failed.

 

I can't remember seeing anyone reporting that the relay was ever the issue. Pretty high probability that it's the sensor.

 

Thanks guys - Part ordered from Amazon, arriving Thursday. Using AutoZone's free loan-a-tool for the sensor socket.

 

Those are good installation tools. They are of no use on stubborn sensor removal.

IMO if the old one seems welded in, the fastest way to get it off is cut it down to a size where a quality impact deep well will fit and have at it with a cheater bar or impact gun.

 

Thank goodness for the rust-free South. I let the PB blaster soak in for about 10 minutes, and with little effort it came unstuck using the sensor socket. I unhooked the battery and cleaned the MAF since my hands were already dirty. CEL gone. Thanks guys.

 

after resetting my cel with p1150 to see if might just be an error the light came back shortly after. since i had b1s1 changed a couple years ago, i assume it's now time to change b2s1 since these parts do fail after time? i had rough idle problems a few months ago and sprayed some carb cleaner (wasn't able to get the iacv off), and have probably never changed the air filter before. what's the likelihood the problem is one of the latter two and not the sensor?

 

With identical sensors on each bank, if you are willing to swap them and see if the problem moves, you will confirm it is the sensor. Just sharing an option ,,, removing the sensor can be a nightmare too.

Salim