DTC P0138 O2 Bank 1, Sensor 2 (2 Viewers)

[CrusrDug]

Thought this would be easy! Replaced the downstream (heated oxygen sensor) on drivers side and DTC came back. Only thing I didn't do was disconnect battery, but I did reset DTC's.

Any ideas?

Thanks!

 

[CrusrDug]

I tested both the old and new sensor with an ohm meter and they both measured between 11 and 16 ohm's. It's looking like it's not the sensor.

I do have another code of C1201, but i cant find anything about the code.

I have read about a hundred posts on O2 sensors, but nothing directly related to my P0138 code. There also seems to be some conflicting information about which sensor it is from this site http://tlcfaq.com/main/2012/09/oxygen-sensor-o2-part-numbers-and-replacement/ but the parts guy at my local dealer said the bank 1, sensor 2 for a 2006 is definitely the oxygen sensor on the cat and not the air fuel upstream sensor.

 

[CrusrDug]

Anybody? I'm at a loss here.

I have checked relays since last post and they seem to be working. Just grabbing straws at this point. This weekend I will clean MAF and try to do some ground testing comparing one side to the other. I will also swap sensors side to side to see if I happen to have bought a bad one, but I highly doubt it.

 

[Sandroad]

On the O2 sensor, I wonder if there is a bad connector or damaged wire? It looks like you replaced the right sensor, but if they are the originals, why not just get a second new one instead of swapping if you're going to all the work anyway? On the unknown code, did you ask Google?

 

[CrusrDug]

I looked up the c1201 code on the scanner website and it said fuel pump relay circuit. That's why I was playing with relays.

That's a good point on the sensor, but I already feel like I wasted money. These downstream sensors are super easy to change.

 

[CrusrDug]

Pulled the MAF and it was jacked up regarding the readings. Needless to say I cleaned it, it started testing good and I put it back in. I cleared the codes, so we'll see what happens. If this is it I will kick myself hard. When I went to rescue my wife after check engine came on, I took everything to clean the MAF. But, I then started checking the blogs and everything was pointing to oxygen sensors so I didn't mess with it. I actually really hope this is it, because like I said, I am grabbing straws at this point.

 

[CrusrDug]

Didn't work. Seems like the MAF is working, but I'm not 100% it is working correctly.

Anybody know how accurate the ohm reading is supposed to be? Mine is jumping around, but it is supposed to change with temp as per repair manual. I just don't know how sensitive it should be.

Anybody have a clue or any other ideas to try?

 

[CrusrDug]

Well, it's not the sensor as I swapped them and same code. I have read there could be a leak in the exhaust, I don't think this is likely, but anything is possible. Could be a shorted wire, but I also checked the volt readings at the sensor (key on engine off) comparing one side to the other and it looked to be the same.

Anybody have any helpful experiences you could share?

 

[CrusrDug]

Bump for the Friday crowd.

 

[staggrlee]

Bump for the Friday crowd.

Bank 1, Sensor 2 is definitely your driver's side downstream O2 sensor.

How do I know this? I have P0141 "O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)" tripping on my truck.

I just crawled under there and a snag must have pulled two of the leads loose. I've got a blue and a black wire dangling from the left downstream O2 sensor.

 

[kev301]

If you need more info, i can get alldata or mitchell info and steps to tracking down the problems. So let me know what you need.

 

[CrusrDug]

Kev301- anything you have that a weekend mechanic can do, I'll try. Everything I read gives a lot of things to "try" but they seem all over the place. I was hoping for try this 1st, then this 2nd, but that may be asking too much for this particular issue. All I have is a basic code reader and a multimeter as far as diagnostics go. Thanks.

 

[kev301]

CrusrDug, if you want pm your email and i can make some copies of alldata and mitchell for you or you can drop off a flash drive to my wife cause she works in folsom and i will put it on the drive for you.

 

[CrusrDug]

It was the frickin' front sensor although the DTC was for sensor 2! Shop verified it was a "lazy signal" swapped sensor to other side and problem carried over. Hope this helps someone in the future. I could have replaced all 4 sensors in the beginning for less than what I ended up spending. Plus a lot less time and headache. If you ever get the sensor codes and the vehicle is running just fine, swap both banks of sensors and see if your code carries over.

 

[Max Cruiser]

It was the frickin' front sensor although the DTC was for sensor 2! Shop verified it was a "lazy signal" swapped sensor to other side and problem carried over. Hope this helps someone in the future. I could have replaced all 4 sensors in the beginning for less than what I ended up spending. Plus a lot less time and headache. If you ever get the sensor codes and the vehicle is running just fine, swap both banks of sensors and see if your code carries over.

This just happened to my wife's 07 LX470. Code for downstream, replaced those, tripped again reading downstream. It was the upstream sensor that fixed it. Thanks for this post.

 

[fro20fow]

Same solution for me! Chose to replace upstream 1st and problem solved. Appreciate this thread. Will have to contribute some of my savings to this site.

 

[Weasel06]

This post is spot on. Ended up replacing all four sensors, but this is exactly what happened on my 06 LX470.

 

[80seriesowner]

It was the frickin' front sensor although the DTC was for sensor 2! Shop verified it was a "lazy signal" swapped sensor to other side and problem carried over. Hope this helps someone in the future. I could have replaced all 4 sensors in the beginning for less than what I ended up spending. Plus a lot less time and headache. If you ever get the sensor codes and the vehicle is running just fine, swap both banks of sensors and see if your code carries over.

What sensors because I have the same codes (02 Sensor Circuit Bank 1 Sensor 2) it has the check engine light. Please let me know what specific sensors or part numbers if you can. Please and Thank you!

 

[emiliobarbarigo]

Same issue with 2006 LX 470. I had P0138 - REPLACED both sensors in the rear. NOTHING. Replaced both front sensors with a new one and that fixed it!