The "Service Engine Soon" light is illuminated on my 01 X. It happened the day after I hosed out the engine compartment, so I'm sure the two are related. I disconnected the battery overnight and the SES light went out; only to reappear after a couple of cold starts. Today I went to my friendly Advance and got the code pulled ... "P0140 insufficient activity HO2S bank 1 sensor 2".

From what I've read about OBD-II systems, this code is usually caused by 1 of 3 things ... bad O2 sensor, lack of ground between O2 sensor and block, or open O2 sensor circuit.

So I've got 3 questions about this problem: 1) where is bank 1 sensor 2 located? 2) What is the torque value (ft/lbs) for the sensor? 3) Is it just a coincidence that the code appears after rinsing the engine or is there a problem with getting this O2 sensor wet?

Any advice appreciated.

1) Right side, after the main catalytic converter (the other on that bank is in the beginning of the upper/main cat.
2) 30-44 ft-lbs.
3) http://www.xterraownersclub.com/cgi-local/ultimatebb.cgi?ubb=get_topic;f=45;t=000888

Brent

Same thing happened to mine. I had mine replaced under the warranty. But it was due to me rinsing my engine the night before.

Thanks Brent. I'll check it out tomorrow. Hopefully it's something simple (maybe the pigtail is unplugged or somehow got a little moisture inside).

I've had that happen several times after washing out the engine bay. I normally ignore it for a week and then disconnect the battery overnight. If the light comes back on then I go to the dealer. I've only had it replaced once after about 10 incidents.

Well, the saga continues ...

Yesterday, I disconnected each O2 sensor pigtail. And guess what ... water was inside each of them. A couple pigtails just had some condensation inside the connector; others had large drops of water. I used a hair dryer to dry the male and female side of each connector, then plugged all back up. I went back to Advance for a code reset. About 4 startups later, the SES light re-appeared.

So I disconnected the pigtails again. WTF??? More water inside the connector housings! This time I tapped each connector (male and female side) on a piece of wood to shake loose as much H20 as possible. Then I dryed with the hair dryer. Off to Advance ... this time when they checked the codes I had P0134 and P0140 (2 O2 sensors).

So I grudgingly went to the dealer. They pulled the codes once again and reported P0134 (bank 1 sensor 1) and P0160 (bank 2 sensor 2). The charge to replace both O2 sensors ... $267 parts and $124 labor.

I told the service advisor I wanted to try and replace the sensors myself. I'll keep you posted on my progress.

Couldn't break loose the O2 sensors. I borrowed an O2 sensor socket from Auto Zone's Tool Loaner program, but still no luck. Looks like you have to disconnect the front drive shaft to get to the left bank after cat sensor. Also, I don't have enough extensions and swivel joints to get the correct leverage on right bank pre cat sensor, so I'll take it too the dealer next week.

Thanks for everyone's help. Also Merry Christmas.

Sorry, You couldn't get the O2 sensors out. Sometimes they are a pain in the ass to change out. I took over an hour to get one free one time. They get stuck because of the constant heating and cooling that they go through. I have a question for you. Did you start the engine up and let it warm up for about 5 to 10 mintues. Alot of times that will help in getting the sucker loose. The only thing is that you have to be careful if you get the engine to hot. Another thing that you can use if you have one is an open ended box wrench of the same size. I forget off of the top of my head the size of the O2 socket. I think it might be a 13/15. I'll check in my tool box when I head out here in a couple of minutes. Also a little WD40 helps out or some liquid wrench is another good thing to try.

Just thought I might throw that out there instead of taking it to the dealer and having to pay in case it isn't covered. Just a thought. If you think that is a bad one to chnage try the one coming from the header on a 97 Dodge stratus 4 dr sedan 4 banger. Took 1.5 hours just to hook up the damn pigtail!

Good luck to you and happy holidays.

Dan,

Yeah ... I hate working on exhaust components. They always require a lot of finesse and Liquid Wrench. The last O2 sensor I changed was on my wife's old car (89 Chevrolet Z24) ... it came right out with an open end wrench. No such luck with the X.

My problem with the X is that the front driveshaft is in the way; I can't use my 1/2" drive pull handle. My smaller 3/8" pull handle will actually fit between the U joints, but I can't get enough leverage on the shorter tool. I tried Liquid Wrench and even beat the heck out of my 3/8 pull handle with a brass hammer, but no go.

I could probably get the stupid thing out if I disconnected the front drive shaft and slid it out of the way, but I've never monkeyed with a driveshaft before and don't feel up to the task.

What really pisses me off is everything would have been fine if I had not rinsed the engine. I've cleaned engines on my 90 Cherokee, 89 Z24, and 96 Camaro on several occasions; never a problem with getting H2O inside the weatherpack connectors. Just my luck.

FYI the O2 sensor requres a 7/8 (22 mm) socket.

Thanks for the info on the O2 Size. Good to know when I go to change one out if I do!! Well, good luck to you.

Yep ... you have to disconnect the front drive shaft to remove bank 2 sensor 2 (I asked the Nissan tech how he removed the sensor).

When all was said and done, I actually needed to replace only a single sensor (bank 2 sensor 2). The other sensor (bank 1 sensor 1) did not need replacing (even though it's trouble code was set). I tested bank 1 sensor 1's heater circuit voltage, power circuit voltage, heater continuity, and sensor output millivolts (using a digital meter and backprobe) and all tests looked OK. So I just had bank 2 sensor 2 replaced and all codes erased. The work was done last Tuesday and so far so good (no SES light).

IMHO ... if you are going to wash the engine, do yourself a favor and cover those O2 sensor pigtails with tin foil, plastic, or some other suitable material.