2001 Quest O2 and Knock Sensors

New Topics Forums General Discussion 1999 – 2002 Nissan Quest 2001 Quest O2 and Knock Sensors

This topic contains 11 replies, has 4 voices, and was last updated by  shooper 2 years, 3 months ago.

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    The SERVICE ENGINE SOON light came on for a bit in my 2001 Nissan Quest. The codes pertain the O2 sensor and the Knock sensor. Someone suggested the problem may actually be the transmission. For the most part, I can’t get the van to go more than 45 mph on level ground. Going up hill…….the most I’m able to do is about 30 mph. Was wondering if others have had the same problem and, if so, what the fix was…the Sensors or Transmission?



    Do not pay attention to P0325 knock sensor. Almost every Nissan has that code.

    I believe the symptom of the speed limit is your van has gone into fail-safe mode.

    What other code(s) do you have? There are two O2 sensors, one front and one rear.




    I’m sorry, I don’t remember the codes. I do remember, however, that there was another code that pertained the catalyctic (sp?) converter. Could that be some of the problem? Thanks for responding!!

    Also, fail safe mode??? You’re talking to someone who knows NOTHING about cars. Could you please tell me what that means? Sorry!! But, thanks again!!



    It is easier to diagnose your problem if you have all codes of your car. Sometimes, one code trigger other codes. This means, if you fix the root cause of the problem, all other codes will go away. In your case, you need to get the codes to help you out.

    Fail-safe mode is when the computer believes the car has critical problems and limits the speed of the van to prevent more damages to the engine or transmission.

    I would not start replacing anything without knowing there is a good reason behing the recommendation.




    Is there a way to get the codes if the SERVICE ENGINE SOON light is NOT on? I’m told you can’t!! Thanks!! Lisa



    If the engine light is not on, then, you cannot retrieve any permanent codes, only pending codes. Take the van to Autozone or Oreilly’s to check for any pending codes.

    If you still have a problem in the van, the computer should detect it and it will turn on service engine soon light again.

    One more note: Do not try to speed up the van if the van is limiting the speed. Fail-Safe mode is to prevent costly damages.




    I took the van to Autozone and it pulled the following pending codes: P0420 and P0325….Catalyst system below something??? and Knock Sensor. Any suggestions? I think one of the sub catagories for the 420 stated something about “front something or other” so I’m thinking that could be the front catalyctic converter???

    Thanks so much for the info!!




    The code you need to fix is P0420. It indicates the catalyst is not able to store enough oxygen.

    Possible causes are: (in order)

    1. Warm-up three way catalyst
    2. Exhaust tube
    3. Intake air leaks
    4. Injectors
    5. Injector leak
    6. Spark plug
    7. Improper ignition timing

    The quickest way to check the catalyst is taking the van to your Nissan dealer. They can use Nissan’s scanner to monitor the O2 sensors readings. If you want to do some Do-It-Yourself troubleshooting, then do the following:

    1. Check exhaust tubes and muffler for dents or cracks. If OK, search for leaks in exhaust piping before the catalyst. Replace exhaust tube(s) if found any damaged.

    2. If all pipes are ok, proceed to search for air leaks after the air filter. Repair leaks if find any.

    3. If no air leaks are detected, check the engine timing. Adjust if necessary. If timing is OK, check injectors. (For this, I recommend take the van to a Nissan dealer)

    4. If injectors are OK, replace spark plugs, ignition wires, distributor cap and rotor. (If the van is high mileage (over 100K+) and you have not replaced these parts or replaced with wrong parts, replace them with correct parts.

    5. If everything above is in good working condition, you need to replace the warm-up three way catalyst.

    There is a very small chance the front O2 sensor might be going bad too. However, the computer is not reporting code P0133.

    If all above is OK (good working condition) replace the three way catalyst. It is the located in the center of the van.

    I have given some tips based on the few information you have provided.

    By the way, How many miles are in your van?




    118,000K approximately. Thanks so much. I’m going to give this info to my son-in-law, who is going to be working on it for me. I appreciate the info!



    Your van is due for:

    1. Timing belt replacement (including water pump and belt adjuster)
    2. Spark plugs (use same as original)

    Very wise to replace also, but you can wait on these if you don’t have the money:

    1. Spark plug wires, distributor cap and rotor
    2. I would definetely include the replacement of plenum gaskets and throttle body gaskets
    3. Replace valve cover gaskets
    4. Replace coolant
    5. Replace coolant hoses (2) to throttle body
    6. Replace oil pan gasket



    Nanaof4, I agree 200% with Pedro’s last comment,

    “If all above is OK (good working condition) replace the three way Catalytic converter.”

    Been there Done that..exact symptoms were on my 2004 Quest and after many suggestions and banging my head onto the several walls, finally the dealer was able to pinpoint the problem with the Catlytic converter and the exhaust tube.
    What actually had happened, at around 100K miles the upstream catalytic converter (1 of 3) started to shed its inner linings and lodging into the lower exhaust tube resulting restricted exhaust flow, and the end result… unable to drive uphills or at < 45 mph the most with temp gauge gone hiking, most pre-symptoms were noticed by my wife who is the main driver, and some of the symptoms included rough idle, rattling as you gas pedal from stops, clunking noises in the engine. And obviously the same CEL warning on the dash with same codes for the “Catalyst efficiency below threshold” along with P0420. Stealer quoted me for $2400++ for the(Cat and the exhaust tube $1860)+ $640 labor. Since there aren’t any after market subtitutes for this model at least at that time, I was lucky to have the final try myself by removing the exhaust tube and banged it with the hammer followed by mallet for about 1 1/2 hr and got out 1600 grams of precious metals withouT the precious price;), i left alone the cat as is and reconnected it and since put on 11,000 miles and knocking the wood. Instead of $2400 it cost me 4 HOURS + $44.29 worth of propane torches to heat the tube and plenty of elbow grease…and I can’t complain anymore, hope that this helps in your troubleshoot. Looking forward to hear back from ya, AND NO NEED TO WORRY ABOUT YOUR KNOCK OR O2 SENSORS, CAT IS YOUR MAIN PROBLEM. 2004 Quest SL



    Hi i was wondering if i could get a little help. My car keeps reading bank 1 o2 sensor not detected. My husband has replaced it twice as well as the other o2 sensor. Any suggestions

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