# Engine Light on



## bocondo (Dec 8, 2005)

I have 97 Nissan Altima, it has engine light on when I went to Auto Zone for diagnosis they gave me OBDII Code P0141. I searched the web and found out it is for "Rear H02S Heater, Bank 1"
What exactly it means? Is it for O2 sensor? If I replace O2 sensor will the light be reset automatically? Please help.


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## LONDONDERRY (May 19, 2004)

bocondo said:


> I have 97 Nissan Altima, it has engine light on when I went to Auto Zone for diagnosis they gave me OBDII Code P0141. I searched the web and found out it is for "Rear H02S Heater, Bank 1"
> What exactly it means? Is it for O2 sensor? If I replace O2 sensor will the light be reset automatically? Please help.


Yup its the O2 sensor that needs replacing. You'll have to clear out the codes. If you don't have it eyt, purchase the haynes manual and it xplains on how to replace the O2 sensor and clear out the codes. 

Frank


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## WATSON1 (Jul 9, 2005)

P0141 is a malfunction in the rear oxygen sensor heater. The causes are either a poor connection or the oxygen sensor is defective. 

Replacing the rear oxygen sensor is not difficult. It is located behind the catalytic converter, so the car must be put on jack stands. Disconnect the cable, unscrew the sensor using a socket made for the job, wipe anti-seize paste on the threads of the new sensor, screw it in and tighten it, replace the cable, done! 
You can take it back to where you got the codes pulled and have them clear it out.


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## Darktide (Jul 29, 2004)

Also, most aftermarket O2 sensor companies actually put the anti-seize compound on their for you. And please don't forget to not touch the "head" of the sensor, it normally messes it up a little. When taking the sensor out a wrench will work just fine, the O2 sensor socket isn't needed, (and if you want to make you own socket just use a proper sized socket and cut a strip down the side for the wire to go). I normally just use vice grips and a hammer :-D its normally stuck in their really good, you may want to pick up a can of PB BLaster and soak it the day before you do the job and then 5 minutes before the job and whack it with a hammer gently to loosen it. It should help you out a little. Good luck with it.


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## jovanni (Mar 29, 2005)

so on the o2 sensor ,the braided steel cable thats connected to the sensor,mine is cut in half due to salt rust etc.do i replace the whole sensor?


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## gfriedman (Oct 12, 2005)

If the sensor is good just connect the wires back together. It'll save ya $100+


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## LONDONDERRY (May 19, 2004)

jovanni said:


> so on the o2 sensor ,the braided steel cable thats connected to the sensor,mine is cut in half due to salt rust etc.do i replace the whole sensor?



You can reattatch the connections if you want. I don't know how long that will last.


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## KA24Tech (Feb 2, 2004)

If the connection is corroded it is time for a new one anyway. I recommend replacing the O2 sensor every 5 years or 60K miles to keep the car running at its optimum.

Troy


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## bocondo (Dec 8, 2005)

WATSON1 said:


> P0141 is a malfunction in the rear oxygen sensor heater. The causes are either a poor connection or the oxygen sensor is defective.
> 
> Replacing the rear oxygen sensor is not difficult. It is located behind the catalytic converter, so the car must be put on jack stands. Disconnect the cable, unscrew the sensor using a socket made for the job, wipe anti-seize paste on the threads of the new sensor, screw it in and tighten it, replace the cable, done!
> You can take it back to where you got the codes pulled and have them clear it out.


Thanks for your reply, I did some more research and I don't think I can change the O2 sensor myself. Can someone recommend me good auto repair shop in North East Philadelphia, who can do good job?


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## Darktide (Jul 29, 2004)

That's not the attitude to have... ask anyone on the forum... you can do it. Its really not too hard. That sensor in particular is easier than the front O2 sensor. Just pick up a pair of car ramps. Drive it up, toss down a tarp and give it a whirl... what do you honestly have to lose? And just remember.... if its snowing... its actually warmer outside than most days  that's the day I chose to take the engine out of my trans am last year... it was a nice blizzard... but I got it out :-D


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## gfriedman (Oct 12, 2005)

Darktide said:


> And just remember.... if its snowing... its actually warmer outside than most days  that's the day I chose to take the engine out of my trans am last year... it was a nice blizzard... but I got it out :-D


Spoken like a true denizen of the northland... well done :cheers:


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## bocondo (Dec 8, 2005)

Darktide said:


> That's not the attitude to have... ask anyone on the forum... you can do it. Its really not too hard. That sensor in particular is easier than the front O2 sensor. Just pick up a pair of car ramps. Drive it up, toss down a tarp and give it a whirl... what do you honestly have to lose? And just remember.... if its snowing... its actually warmer outside than most days  that's the day I chose to take the engine out of my trans am last year... it was a nice blizzard... but I got it out :-D


Thanks for word of advice, I was able to do it myself with the help of a friend, but the engine light is still on. How can I reset it? Will Autozone people will do it?


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## gfriedman (Oct 12, 2005)

bocondo said:


> Thanks for word of advice, I was able to do it myself with the help of a friend, but the engine light is still on. How can I reset it? Will Autozone people will do it?


 :thumbup: Way to go boco!! 

I think it's against policy for Autozone to clear codes but you can ask. Otherwise there are 3 ways you can do it. 1) Unplug your battery negative terminal overnight; 2) with the key on (engine not running) turn the diagnostic switch on the ECM full clockwise wait 2 secs then full counterclockwise wait a few seconds then repeat. 3) Just drive the car - it will clear on its own eventually if the problem is gone.


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## bocondo (Dec 8, 2005)

gfriedman said:


> :thumbup: Way to go boco!!
> 
> I think it's against policy for Autozone to clear codes but you can ask. Otherwise there are 3 ways you can do it. 1) Unplug your battery negative terminal overnight; 2) with the key on (engine not running) turn the diagnostic switch on the ECM full clockwise wait 2 secs then full counterclockwise wait a few seconds then repeat. 3) Just drive the car - it will clear on its own eventually if the problem is gone.


Cool... I am going to try the first thing to unplug the battery nagative for tonight and see what happens. I hope there is no more problems. Thanks a lot for your advice.


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## LONDONDERRY (May 19, 2004)

bocondo said:


> Cool... I am going to try the first thing to unplug the battery nagative for tonight and see what happens. I hope there is no more problems. Thanks a lot for your advice.



Personally, I would reset the ECU using the screw on the side. In doing so you'll learn how to read the codes the next time something comes up, as to depend on someone doing it for you. Plus its much easier that disconnecting a battery terminal. If you have the Haynes book it demostrates on how to do this. If not, go out and buy it, its worth having, trust me.

happy holidays
Frank


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## bocondo (Dec 8, 2005)

gfriedman said:


> :thumbup: Way to go boco!!
> 
> I think it's against policy for Autozone to clear codes but you can ask. Otherwise there are 3 ways you can do it. 1) Unplug your battery negative terminal overnight; 2) with the key on (engine not running) turn the diagnostic switch on the ECM full clockwise wait 2 secs then full counterclockwise wait a few seconds then repeat. 3) Just drive the car - it will clear on its own eventually if the problem is gone.


I have tried 1) unplugged the battery overnight and 3) drove my car for 600 miles, but the light is still on.  What should I do next? Should I try the second one also? Please help.


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## gfriedman (Oct 12, 2005)

You could go to autozone and ask them to check the codes for you. Maybe a different code this time.


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## KA24Tech (Feb 2, 2004)

I have written about how to check the codes on a previous thread;
The ECU is under the front of the console. The trim panel under the very front of the console on the driver's side. The ECU has a diagnostic mode which is activated by turning the ignition to the on position without the engine running and then turning the mode select fully clockwise for two seconds and then turn it back fully counterclockwise. Wait for the inspection lights, which are next to the mode selector on the ECU. All you have to do is read the long and short flashes (the first digit is the long flash(es) and the second set is the short flash(es). To get it out of diagnostic mode just turn off the ignition just make sure the selector is all the way counterclockwise.

Troy


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