Hello,

I have taken some time to learn about a recent code that I got on my 99 RX300. It was a P1133 Code (Bank 1). I was told it is an oxygen sensor but elsewhere I have seen it described as an AF sensor. May I ask which is the correct answer? Does this code specifically refer to the oxygen sensor and if so am I correct it is located behind the engine? Any other input would be greatly appreciated.

Thanks,

Marc

 

whats in the name?

The code refers to malfunction (out of norm) amount of fuel/oxygen in the exhaust [it is a chemical reaction].

Most of the time it is the sensor, but the problem can be any where in the fuel supply to air. Although for air there is a MAF sensor.

How many miles on your RX?

Bank one is the side next to the firewall. There is a DIY (search). The difficult steps are disconnection the connector and loosing the sensor. [what else is left ,,, crawling under ].

I am getting ready to do that myself. Invested in deep offset wrench set.

Q: Can the connector head pass through the box end of 21mm.

I will need the special socket to torque the new sensor in.

Salim

 

The P1133 code is Lexus specific and IS the A/F sensor. (air/fuel ratio sensor) It is indeed the one on the back of the engine and that P code is SPECIFIC to that sensor and is listed as "air/fuel ratio sensor circuit response malfunction". As Salim said, it MAY not necessarily be a BAD sensor, the problem COULD only be showing up there.

 

Is there a way to identify whether the sensor is bad once its taken out?

The vehicle has about 168,000 miles on it.

 

No guarantees, but at that milage, it is a very likely culprit.

Salim

 

So I know this is a really really late reply but I figure it's better to complete the story than leave it open. As Salimshah had stated the code P1133 is for an out of balance in the fuel/oxygen ratio in the exhaust. It wasn't until recently as I was finally getting around to fixing a nagging exhaust leak that was getting worse that I put two and two together.

If I was right then the code would disappear when I replaced the section of broken flex pipe (horrible design by the way). Sure enough when I did the code went away. Evidently the sensor was picking up the increased levels of oxygen from the exhaust leak. The code use to come a go but as I think about it now as the leak got worse the sensor tended to stay constant.

Hope this helps anyone else experiencing a similar problem with this code.

 

Any photos or more details about your flex pipe repair. Where was it, how did you detect it, advice for how to fix it, etc...

 

I did not actually fix the flex pipe but instead was able to purchase that section of the exhaust pipe with a flex section for around $65 on Amazon.com. The hardest thing was getting the bolts off. At first it didn't seem like my simple ratchet was going to be able to take them off. I invested in some PB Blaster, ran the vehicle to heat up the pipe, applied the spray, and waited for the engine tool cool. With some effort they all came off.

 

Thanks Marc,
Interesting problem. Am I correct in assuming you did NOT replace the Bank 1 A/F sensor and the problem went completely away just by replacing the flex pipe? This is confusing to me since the P1133 code refers directly to a malfunction with that sensor and the flex pipe is downstream of it. This would be very valuable trouble-shooting information if that is the case.
Baetke

 

Can you please list the item you purchased to help other members.

Thanks

Salim

 

I think he is talking about this piece:

 

For some reason I didn't get notified about further posts until today. Yes Carguy07, that is the part I purchased. That and a couple of the required gaskets. When I finished unbolting both sides the old pipe literally fell apart in two. I did notice a slight difference between the pipes on the end closest to the engine. The old pipe is slightly recessed to allow the gasket to set into it and I imagine make the the two pieces more flush. The new one didn't have this recessed portion.

 

I was reviewing a old post and realized I didn't respond to Baetke's question. The answer is that yes, I did not have to replace the AF sensor in order for the P1133 code to go away. This code has not surfaced again but interestingly enough I received a P1135 code last month and have noticed some rough idling.