81corolla

Here is a Do-It-Yourself (DIY) thread on changing the air/fuel sensor. You usually have to change it if the check engine light (CEL) is on and the car is throwing codes P0171, P1130, P1150, etc.

I don't want to get too much into whether you need to replace it or not. There are other threads that do that.

My car's CEL went on. I stopped by local AutoZone or Advance Auto and had them read the code. It was P1130 - bank 1 sensor 1. That's the a/f sensor on the back three cylinders exhaust manifold (rear). This DIY will cover replacing the back sensor.

If you need to replace the front sensor, it's similar just in a different spot. :-)

Update #1: sensor locations

Clear diagram of sensor locations:
https://www.clublexus.com/forums/att...sensor-1-3.pdf

Mercilessly stolen from this thread:
https://www.clublexus.com/forums/rx-...ensor-1-a.html

Excellent photos of sensor locations:
https://www.clublexus.com/forums/rx-...af-sensor.html OR
https://www.clublexus.com/forums/rx-...-sensor-3.html

81corolla

Testing sensor:

You can easily test the front air/fuel sensor to see if it's bad or not. The rear a/f sensor is a little harder only because of it's location, but it's not impossible.

When I get some time I'll do a write up on testing the sensor and link to it.

Edit: here's the writeup on testing a sensor
https://www.clublexus.com/forums/rx-...esistance.html

81corolla

Shopping for replacement part:

The Lexus part number for the RX300 air/fuel sensor is 89467-48011. The OEM a/f sensor is made by Denso and the Denso part number is 234-9009. The two are equivalent.

Lexus sells the part for ~$300. Toyota sells the part for ~$200. You can generally find one on eBay for ~$150. I found the part on Amazon for $126 with free shipping; by far the best deal. I ordered it on a Monday and received it Wednesday.

Here is the Amazon part for reference (Sept 2009). If this link dies in the future, just search Amazon with "Denso 234-9009" and you'll find it assuming they still stock it.

http://www.amazon.com/Denso-234-9009...3794019&sr=8-1

Note: Amazon's cross-reference chart doesn't list the RX300, but don't let that stop you. The part number is correct.

81corolla

Overview

Put car on ramps night before
Spray plug with WD-40 or PB Blaster
Unplug old sensor wire
Remove old sensor
Insert new sensor
Plug in new sensor wire
Reset CEL

81corolla

Put car on ramps

I put the car on ramps the night before I made the repair. That night I sprayed the sensor with lots of WD-40. Others use PB blaster.

Keep in mind that running the car just for a few seconds to put it up on ramps will cause the exhaust manifold to heat up and you'll want to wait for it to cool off before beginning work.

81corolla

Unplug sensor

The previous photo shows the a/f sensor wire plugging into the socket. I found it easier to get to the plug from the top through the engine compartment. Just reach back and press the little tab down and pull the plug out. Hopefully it won't be stuck on too hard.

81corolla

Photo of sensor unplugged.

81corolla

Tools

There is a couple of tools one can use to remove the sensor. I used a 7/8" wrench with a nice elbow in it as shown in the photo at the far right. I found the elbow to be very helpful.

To the left of that in the photo, is a sensor socket with a breaker bar. The socket is open on the side so it can get around the wires. The socket is 7/8" as well.

The last tool in the photo on the far left is a straight 22mm wrench. Although the tool fits, I was unable to get it to unscrew the sensor. There's a metal bar in the way which is avoided by using the wrench with the elbow in it.

lexus114

Great post!!! Thank you!

81corolla

Unscrew old sensor

The sensor plug fits through the open end wrench side. Then unscrew sensor.

Hopefully it won't be stuck on too tight. If so, you may have to use heat with a torch.

81corolla

The part included a small tube of anti-seize compound. Put it on the threads of the new sensor and rub it around. Try to avoid getting on sensor itself.

81corolla

I put it on the threads of the socket on the manifold, but I wouldn't do that again. Kind of a pain to get the new plug in without hitting the sides and getting compound on the new sensor.

81corolla

Screw in and tighten up the new sensor. The sensor should be snug - no need to crank down on it - it's not going anywhere.

81corolla

Plug the new sensor wire into the socket.

81corolla

To reset the CEL, pull the ECU fuse from the engine compartment for about 10 minutes. You can actually do this at the start of the work.