Hi, everybody;

Happy New Year.

I'd like to share with you my experiece of fixing a Check Engine light problem caused by the O2 sensor in my 1999 Nissan Quest. I believe it will be useful to people having similar causes of the problem. At a minimum, it will give you a top list to check even though the root cause of the problem is not the same as mine.

My Check Engine light turned on over a month ago. My mechanics told me it was caused by bad O2 sensors (error codes 0135 and 0141) and knock sensor (0325). Replacing the two O2 sensors is relatively cheap, about $300 to $400. But for the knock sensor you are talking about $700 to $1000. I did not let him do it partially because of the high cost and partially I was uncomfortable about the fact that he reached the conclusion based on the readings from his scan. I thought he would test the O2 sensor at a minimum.

I won't go through how this negatively impacted my holiday and how much time I spent on searching Internet for clues and fixes. The Haynes Repair Manual did a very poor job on this. I got it fixed after I got the 1999-2002 Nissan Quest Factory Service Manual.

The fix was so simple that any not-bad mechanics could not charge you over $10 besides the $90 diagnosis fee he will charge you.

The problem was caused by the broken O2 sensor fuse in the fuse box. You just need to take out the bad oen (7.5 A) and replace it by a spare fuse inside the fuse box. You can finish this in 1 minute.

The following are the tools recommended for checking similar problems:
1. order a simple scan. It cost me $33 from www.autonostics.com. It'll tell you the trouble codes.
2. order a 1999-2002 Nissan Quest Factory Service Manual. I got it from eBay at $10. You can contact importautowork@yahoo.com if you want to order it from the same guy I ordered from.

OBD II codes 0135 and 0141 basically say that there is no voltage going through the O2 sensor heater or the sensor heater is gone, i.e. no resistance through the heater.

The knock sensor trouble code (0325) is collateral damage from O2 sensor problem in this case. It may go away after the O2 sensor is fixed.

The fuse box is located underneath the driving wheel, on the left hand side.

The down stream O2 sensor is located close to the oil pan in case you are looking for it.

Good luck.

Sean