Knock Sensor

[927max]

My car has a check engine light for more than a month and the autozone diagonised with knock sensor and oxygen sensor problem. My question is how accurate they are? If I go to pepboys or other they are going to charge $65 for diagnosis what should I do? should I get it checked again before replacing it or by buying the part?

I have a muffler problem too it "groans", so I am not sure if I am loosing power due to muffler or knock sensor? Please advice.

[MTZI30]

Well did autozone give you specific trouble codes? What do you mean the muffler groans? Unless the exhaust is really banged up, you shouldnt have any loss of power.

[927max]

Yes they gave me codes and also gave the description printed, nissan car was not listed but other llike toyota, mazda etc and it said knock sensor problem and oxygen sensor problem.

[loystock]

It's never a good idea to run a car with CEL for extended period of time as it could lead to more problems.

The faulty Knock Sensor will not turn on the CEL but will generate a fault code (P0325). This will lead to lousy acceleration due to ignition timing retard (to avoid knocking).

The CEL is due to faulty O2 sensor. You need to provide the code as there are 3 O2 sensors in a 97 Maxima.

As for the exhaust groan, you may have a leak/hole - check the exhaust pipe, particularly at the joints and welded areas..

[927max]

The codes given by Autozone are P0325 and P0136 - Nissan car is not listed in the description but toyota, maxda and other cars are listed with knock sensor and oxygen sensor problems. Yes there is lousy noice during acceleration but I don't know if it is coming because of knock sensor or due to exhaust pipe
Exhaust groan, yes there is leak at the joint when I got it diagonised they said they need to replace the whole exhaust pipe as the joint is rusted and temporary fix cannot be done.

[loystock]

The faulty KS (P0325) will cause the ECU to retard ignition timing to avoid pre-ignition/knocking. Hence, acceleration is affected. The sensor can be replaced without removing the intake plenum, but requires a certain level of ingenuity. The cost of KS at dealership is $150 or more but you can buy OEM KS from eBay for @ $50. Avoid the cheap ones as they don't last long. Here's a YouTube video on how to replace the KS, courtesy of "boredmder."

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

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

DTC P0136 indicates defective Rear O2 sensor. The Bosch OEM sensor is $150 or more at the dealership/online. An OE-equivalent from NGK/NTK, P/N 24630 is available from NICO sponsor, NGK.com, a.k.a. "sparkplugs.com" for @ $73. You can also try Amazon.

Here's a link on how to replace the Rear O2 sensor.

http://www.moodym.com/maxima/cullen/cullen.html#knock