Hi everyone, has anybody experienced with the problem below?
Vehicle: 2000 RX300 with 50K miles.
The CEL is OFF when gas tank is full but ON when the gas goes below at about half of the tank. It has been acting that way in last 2 months. It gave code P1130 when the light was on.
I've tried to replace with different fuel cap from another family member's Toyota car but didn't see any difference.
Please help if you can? Thanks.

 

I assumed you have tried resetting the CEL and still the same issue.

Recently we covered a P1130 from start to finish, https://www.clublexus.com/forums/sho...d.php?t=287550 and is related to the rear A/F sensor, but it does not necessarily indicate a bad sensor (since yours comes on and off).

However, given that you mentioned the gas tank, when you remove the cap, you hear a woosh sound?

On an outside chance, there could be a fuel pressure problem. Sometimes bad gas, sometime injectors, fuel pump. However there, you would see P04XX errors, but mainly the situation you describe starts first with a gas cap.

 

Thanks Lexmex.
I did not reset the CEL. It turned off by itself when I filled up the gas. When the gas level dropped just about below 3/4 of the tank, it's on again. I started to notice that in my last 5 fill-ups.
Yes, I do hear the woosh sound when remove the cap.

 

Before spending money on an A/F sensor, I would drop in on 1/2 a tank one bottle of Techron fuel injector. A possiblity here is that there is a fuel pressure issue when the tank drops to the level you indicated and there could be a blockage in one or more of the injector. Techron can help around the pump area as well, but it is more likely to have blockage around the injectors (bad spray pattern). Such blockage would slow fuel delivery and of course at a certain tank/fuel pressure level, the A/F ratio would go out of whack. I would hate to see you have to buy a new A/F sensor, but as was shown in the other thread I posted that indeed occurred.

 

Forgot to mention, I've put 3 bottles of the Lucas Fuel Injector Cleaner (5.25 oz.) in my last 3 tanks. But I'll try the Techron in the next tank. I've just switched over to Shell 93 octane from Costco gas since the CEL came up.

 

Lucas is good stuff, but I found the Techron can attack some types of deposits a little better. Remember to run at least one tank afterwards without the cleaner. Injection cleaner can sometimes by itself cause an issue in the combustion process when cleaning out deposits, but after it passes through the system, no issues.