P0141 & P0325

[nosaku]

I have a 1999 Nissan Maxima. 6 months ago I got the Check Engine Light and I went to Nissan Dealer. He diagnosed it as P0133 and replaced the B#1 O2 Sensor. The car was running fine and recently (10 days ago) I got the Check Engine Light again and it stayed on. I went to Auto Zone and they gave me the codes P0141 and P0325. What could be the problem? The car is running fine but am I damaging it by driving it like that? I drive around 25 miles per day. How much does it take for repairs if I have a problem? The Nissan Dealers are way too costly.

Regards,
Satish.

[MTZI30]

Im pretty sure po141 is a 02 sensor fault. I think your car has like 4. Usually they last around 100k+. I had the same code and turns out Infiniti says you should replace both post catalyst 02 sensors at the same time. PO325 is a knock sensor, i googled that one.

[loystock]

You may have 3 or 4 O2 sensors in as 99 Maxima (transition between 4th and 5th Gen). There are 3 sensors in cars with Federal Emission Configuration while those with CA (California) Emission Configuration have 4 sensors. The OEM Bosch O2 sensor is @ $150 each while an OE-equivalent from NGK/NTK is @ $50-90, depending on the location. If you are mechanically inclined and have basic hand-tools, you can do it yourself. But usually, an O2 Sensor Socket (@ $10) is needed to protect harness from damage.

The KS sensor (P0325) is not easy to replace, especially in cars with CA-Configuration. I have done it on a 99 I30 with CA-configuration but I have to get a longer mounting bolt and modify it to make it work. You don't have to remove the intake plenum but you may get bruised along the way. The KS is @ $150 from the dealership but you can get OEM-Nissan part from eBay for <$50. Do not buy the cheap ones as they won't last long.

I'm not sure whether you are willing to tackle the KS replacement. Just to give you an idea, here is a YouTube link on KS removal from a Maxima with Federal Configuration courtesy of "boredmder."

http://www.youtube.com/watch?v=R2ntaxi7 ... re=related

http://www.youtube.com/watch?v=fPIMOIwL ... re=related

[nosaku]

Thank you very much MTZI30 and loystock for your quick response and valuable inputs. I may not be able to do it myself as I have zero knowledge about car mechanics. Probably I will take it to a dealer or some local mechanic.

Just to get the clarification... do I need to replace both O2 Sensor and also the Knock Sensor?

Regards,
Satish.

[MTZI30]

Well you should have a code specific to the faulty 02 sensor. You can just replace that one. However myself, i like to just cover my bases and replaced both of my post cat 02 sensors since im gonna hold on to my car for a while. Ya sounds like you do need to relpace the knock sensor, the stealership will prolly charge a lot more then a local mechanic. Maybe search the yellow pages for a good independent shop.

[nosaku]

Thanks a lot again. Yes "stealership". I went couple of times to Nissan dealership near my place and already they ripped off my two paychecks. I will find a local mechanic shop. I guess I need to it fast, as my car seems to be hesitating to start for a second or so and then starts. I think it is dying.

Regards,
Satish.

[loystock]

Again, we have to know if you have Federal or CA Emission configuration. To find out, pop the hood and on the underside of the hood, you will find a white sticker - CATALYST: If it states that it complies with CA Emission, then you have 4 O2 sensors. Otherwise, only 3 sensors.

Federal configuration has 2 front O2 sensors (on the exhaust pipe below engine) and 1 rear O2 sensor (mounted downstream of the main catalytic converter). The CA configuration has 2 front sensors and 2 rear sensors mounted on the Pre-Cats (2 ea). There is no O2 sensor in the main 'cat.'

The Bosch OEM O2 sensors are rated at 100K miles but it does not necessarily mean that they will fail at that mileage. Most of them last beyond 100K miles, especially if the car is maintained properly and has used Tier 1 fuel. An O2 sensor may fail prematurely in case of contamination (oil, etc) or driving the car for extended period with 'rich' fuel-air mixture. I replace O2 sensor 'as failed.'

It will cost you a lot to have it fixed at the dealership. Even though you already have the trouble codes, they will insist on running their own diagnostic which will cost you @ $60. But then, they usually give up to a year warranty on the repair. You can save a lot of money if you buy the parts yourself (we can direct you where to buy them) and have them replaced by a trusted mechanic. You have to ask relatives/friends for a reliable shop that handles Nissan cars.

Again, the KS can be replaced without removing the intake plenum. It will cost you more if they insist on removing the plenum to replace the KS (more labor charges and gaskets have to be replaced.

[G-justin]

Again, we have to know if you have Federal or CA Emission configuration. To find out, pop the hood and on the underside of the hood, you will find a white sticker - CATALYST: If it states that it complies with CA Emission, then you have 4 O2 sensors. Otherwise, only 3 sensors.

Federal configuration has 2 front O2 sensors (on the exhaust pipe below engine) and 1 rear O2 sensor (mounted downstream of the main catalytic converter). The CA configuration has 2 front sensors and 2 rear sensors mounted on the Pre-Cats (2 ea). There is no O2 sensor in the main 'cat.'

The Bosch OEM O2 sensors are rated at 100K miles but it does not necessarily mean that they will fail at that mileage. Most of them last beyond 100K miles, especially if the car is maintained properly and has used Tier 1 fuel. An O2 sensor may fail prematurely in case of contamination (oil, etc) or driving the car for extended period with 'rich' fuel-air mixture. I replace O2 sensor 'as failed.'

It will cost you a lot to have it fixed at the dealership. Even though you already have the trouble codes, they will insist on running their own diagnostic which will cost you @ $60. But then, they usually give up to a year warranty on the repair. You can save a lot of money if you buy the parts yourself (we can direct you where to buy them) and have them replaced by a trusted mechanic. You have to ask relatives/friends for a reliable shop that handles Nissan cars.

Again, the KS can be replaced without removing the intake plenum. It will cost you more if they insist on removing the plenum to replace the KS (more labor charges and gaskets have to be replaced.

Can any of the o2 sensors possibly trigger the knock sensor in a 99 i30??
just went to advanced auto and had them pull the codes they are po325 bank 1 knock sensor and po 138 bank 1 sensor 2 high voltage just wondering what info you could give me on these codes and if one triggered the other if so whick one should be replaced 1st the guy at advanced said replace knock sensor 1st but a mechanic that i go to said the o2 can trigger the knock sensor because it makes it run rich or lean???

[loystock]

I don't recall any incident of a Rear O2 sensor failure triggering a KS (P0325) code. The best recourse is to check the KS resistance, 550 K-ohm (spec is 500K-620K-ohm). Connector for the KS is towards the front, driver side. If resistance is out of spec or open, replace it.