I need help! I have exhausted about every option I have to resolve this dashboard light. I have an OPDII reader and I keep getting an error code P0157. I reset it and it comes back after just a few minutes. I know this relates to Bank 2, Sensor2 on my exhaust. I have tried changing the sensor (3 times now) and I've tried other trouble shooting I'll describe below. First I'll give you just a little background; It's a 2005 ES330, I purchased it new and it now have about 250k miles. It's in pretty good shape and there is some sentimental issues with it.

I did develop an oil lead on the front valve cover (drips right on the B1S2 & B2S2 connector) and didn't fix it for a while. Even with 250k miles, I don't think I've ever changed the O2 sensors. I finally fixed the oil leak and spent a day cleaning all the old grime and oil from the engine. Was a lot of work but the engine looked great when I was done. I purchased a new O2 sensor and installed it. It kept the light off about 3 months. It was an "import" and was still in warranty so I returned it. This time I spent the $$ and got a Denso. Installed and didn't solve the problem. I returned it and got another Denso. Installed and still no fix! So I started reading and watching videos.

The original sensor looked very clean. I spent a lot of time really examining and cleaning the connectors. When I installed new sensors I used dielectric grease. The connectors looked really clean and they didn't seem damaged at all. I plug my scanner in and I could see I was getting almost 0-volts outgoing. There was occasional movement but not much. I have ohm'd each sensor and get impedance on the heater portion. I later checked the heaters by taking them out of the exhaust but leaving them connected. It took a few minutes but they did get to hot to touch. I've pressurized the exhaust system and only located one very small leak (B1S2 sensor). I corrected that. I tested the new sensors (and even the old original one) with a volt meter and a torch. Voltage looked fine. I have tried to get a voltage reading on the connector that comes from the PCM and I get no voltage reading. I tried this same test on B1S2 and got the same results. I tried this test with the key off, the key on and then with the engine running. No voltage on either B1S2 or B2S2.

I then installed both sensors (B1S2 & B2S2) in their exhaust ports after warming the engine. I left them electronically UNCONNECTED from the car. I used my volt meter and got about the exact same reading to my volt meter from both sensors. After connecting them and using my scanner, I still got zero voltage showing.

I'm of the opinion the sensors are good, the contacts are now good and clean and there are no exhaust leaks. What am I missing?

 

Hello,

Considering that everything else was checked already, try making sure that the wiring to the sensor is intact. Below is an ECU connector pinout, check the continuity between Pin 3 on the O2 sensor, and Pin 29 of the ECU.



If you don't already own one, I would suggest investing in a basic oscilloscope, below is a link, the Narrow-Band Downstream sensors produce their own voltage that can be measured directly from the sensor. If the wiring test won't yield any results, try using the oscilloscope to make sure that the signal is indeed present on the sensor, then do the same on the ECU. The car will have to be at operating temperature to get any readings, so make sure to be careful.


P.S. Such huge swings on the Bank 1 readings indicate a catalyst that no longer does its job, it will need a replacement in a near future, I wonder if that has something to do with the problem you are experiencing..

Hope this helps and best of luck!

 

Your willingness to help is appreciated. The info and diaghrams were something i was hoping for. Ill get that impedance checked and see if I need an oscilloscope.

One thing I didn't mention; the screen capture I posted was taken while I was driving (stop & go). I hope with this info it means my cat from bank 1 is still stable.

 

Only one way to find out - while stationary at idle, check the readings again, they should be as close to 0.45V as possible, the more fluctuation you get, the worse a catalyst is doing, though I wouldn't worry about it too much, the car will notify you should there be a problem.

Hope this helps and best of luck!

 

Oscilloscopes are wonderful things.

But they do require a minimum threshold of knowledge to get the best out of them.

In the context of this discussion, we'd be wanting to look for (a) "verifiable" sensor voltage output and (b) injector signal waveform.

Once you learn how to get access to your ECM and then learn how to connect the relevant pins for diagnostics with an oscilloscope, your problem solving skills will go through the roof.

 

Sounds like a wiring issue in the harness from the sensor plug back to the ECU. Look for torn or damaged areas. I accidentally tore one of the wires while replacing a Bank 1 sensor and had to remove the whole intake to repair the wiring. Almost cooked the engine while test driving it with a severe misfire on Bank 1.