Mazda Millenia This sedan, the flagship luxury sedan, offers both a naturally aspirated and supercharged model, so you can have your luxury, and, if you have a need for speed, big horsepower.

P0421

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  #1  
Old 06-18-2007 | 10:02 PM
2000grnS's Avatar
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Default P0421

i cant find which o2 sensor it is from the front of the car if anyone could help plz low bank 1 need help..............
 
  #2  
Old 06-19-2007 | 08:36 AM
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that is the REAR bank. and it would be the post(after) pre cat sensor. you can get at it very easily from underneath. however, you should first log the date of the code, then just erase it. more than likely it will come back, but not for some time. then, each time you erase it, if the duration gets less and less, you need a rear pre cat. the sensor wont do it. while there are a couple of slightly illegal ways to get rid of the code, replacing the pre cat will also net you some power gains, you will feel the difference.
 
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Old 06-20-2007 | 05:28 PM
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could you tell me if its the left or right when your looking under the hood
 
  #4  
Old 06-20-2007 | 06:27 PM
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ok, the hood is up, and you are standing in front of the car, right between the headlites. the motor sits in there side to side, or transverse. i have no idea which bank is #1, that is a term invented by us car wannabes. foreign car TECHNICIANS(not mechanics) only know right or left bank on a "V" motor. in this case, p0421 is code for the right bank, which is the one in the rear. the left bank would be the one closest to you. the right bank always has cyl #1, same as in europe.
 
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Old 07-22-2007 | 11:29 AM
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light keeps going out then coming back on is this a very common process and how hard is it to replace o2 sensor need a lil help
 
  #6  
Old 09-07-2007 | 06:56 AM
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Default RE: P0421

Keninn, I'm a little confused as to your definition of left and right. The engines left would be the bank at the rear, and the right would be the bank in the front, wouldn't it?

And, as a side note, I can get the cat for under $75 and have it hung for about $100. That would bejust a tad cheaper than therear post-cat O2 sensor($200-250).
 
  #7  
Old 09-07-2007 | 08:34 PM
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correction. you can get the WRONG cat for 75. that would be what is called the main cat. there is nothing wrong with your main cat. the 0421/31 is the PRE cat. which is part of the exhaust manifold. and no way no how will you get the pre cat "hung" for 100. go back and do your homework.

also, your left and right interpretation would be correct for a LEFT hand drive car. however, in germany, as in japan, the cars are RIGHT hand drive. but hey, you can call it whatever you want, it's your car. and look at it this way. after you actually buy the correct part, you will also have the part for the other side.
 
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