Code P0135 Problem On '03 Rx300

[RX300LMR]

At 65,000 miles my VSC/CEL lights stayed on so I had local Auto Zone read codes, 1st was P0135 for O2 Bank 1 Sensor 1. So to confirm the troubleshooting we swapped out with 2nd front sensor under the car and brought back to AZ again and sure enough, code changed to P0136 for Bank 1 Sensor 2. Conclusion was a new sensor was needed so we bought the Denso universal, soldered and replaced original front sensor. Went back to reset at AAP and of course it still throws the P0135 code.

Knowledgable manager at AAP said universal wasn't wide band and maybe that could be my problem, so I bought a Bosch wideband replacement sensor. Went through the same ritual, reset and it still throws the same code and lights stay on. Meanwhile, my mpg hasn't changed and car still running fine.

Called a few Lexus dealers and they said only the original Denso A/F Sensor #89467-48011 would shut off the CEL/VSC lights. So I picked up the part from the local Lexus dealer($211) and swapped out Sensor 1, disconnected the battery for an hour and lights came back on. I couldn't find the thread with the fuse trick but I will try that too.

Today we brought back to AAP and reset using the scan tool, but sure enough lights came right back on, again throwing P0135 code. Needless to say I'm very discouraged since I was hoping to avoid giving the dealer another $150+ just to use their scan tool. Any thoughts as to what to try next? NH has emissions so I can't pass inspection.

I welcome and appreciate any advice. I've spent many hours researching on this particular forum and was surprised to see many peo w/same problem at similar mileage, but I can't seem to find out the next step. Thanks.

[lenore]

Read this post, may be your problem, apparantly the heaters are wire in series.

I have a '98 Avalon and got the same P0135 code when checked at Advance Auto Parts yesterday. I purchased the Bosch "universal" O2 Sensor for $ 64 as opposed to the $147 "wired to OEM" special. I agree with Mike that the wiring connection isn't too tough so save some $ and buy the universal unit. However, the rub I had was knowing which sensor is Bank 1, Sensor 1. Going to my Haynes book shows O2 Sensor with Bank 1, Sensor 1 being the front sensor easily seen when you open the hood and look down on the exhaust manifold. But here is the kicker, the Avalon has two sensors, Bank 2 sensor 1 is the other with the heater circuit jumper together. Bank 2 sensor 1 is between the engine and firewall, you can see better on driver's side when looking for it. Going to the electrical wiring diagrams in the back of Haynes shows that if either sensor heater circuit faults I believe you will get the infamous P0135 code "Bank 1 Sensor 1 heater circuit". Love those electrical diagrams. So disconnect the sensors at the connector and pull out your volt meter. Check the heater circuit on each sensor before you replace the wrong one. Check the terminals where the 2 black wires connect, no polarity on the heater circuit, for resistance (ohms) should be 11 to 16 ohms when engine is cold. For instance, I got 13.2 on the front one and the back showed OPEN. Replaced the back one and then went back to Advance for a PCM reset to clear the "Check Engine" light

[RX300LMR]

Thank you so much for your reply, we tried the advice and checked the voltage on the sensor underneath the car that we thought was fine and sure enough, the heater circuit was OPEN. Due to the P0135 code it didn't occur to us that the lower one could be the problem. We put the new OEM one under the car and put the original factory sensor back in place near the exhaust manifold, pulled the EFI fuse and now the Check Engine Light finally shut off!

I am relieved to say the least, but now the VSC light is on by itself - any thoughts as to why? Checked the brake fluid and it's just above the min line but that is an easy fix. I couldn't find any posts about VSC only light being on without the CEL. Anyone know if I can pass inspection with the VSC light on - or will it shut off on it's own?

Can't thank you enough for taking the time to reply, I really appreciate it - and have a great holiday!

[lenore]

Maybe there is some debris on one of the speed sensors located at each wheel. Envolves taking each one off and cleaning. Located on the wheel hub. you will see wires going to each wheel. Good luck.

[wwest]

Maybe there is some debris on one of the speed sensors located at each wheel. Envolves taking each one off and cleaning. Located on the wheel hub. you will see wires going to each wheel. Good luck.

That wouild most result in an ABS fault indication..........also.

[RX300LMR]

Thanks, ABS light is definitely not on, just the VSC. I'm bringing to AZ tonight to see if there are any new codes, I looked through the error code list and didn't recognize anything obviously relating to VSC, but we'll see what happens.

[mikey00]

Might be worth a try to pull the negative battery connection for a few minutes to reset the light. If it doesn't come back on, your good. If it does then pursue the codes, but I think you are right about none relating to just the VSC.