O2 Sensors?
 

I replaced my o2 sensors in my 2000 explorer 4.0 OHV about a month ago. Its been fine today my check engine light came on im getting code P0171 and P0174 system to lean bank 1 and system to lean bank 2. Are my o2 sensors bad again? I replace all 3. I used bosch sensors are they garbage? Or can it be something else? please help

RE: O2 Sensors?
 

PO171/174 can be set from a few problems.. Vacuum leaks ect.. But, as a first step, clean the Mass Air Flow (MAF) Sensor with a 'spray only' of throttle body cleaner (not carb cleaner) with the extended tube tip installed to direct the spray pressure at the wire/s..ThePCM utilizes a heated wire within the sensor and monitors intake air flow over the wire as it 'cools' for a signal for a given throttle angle and volume of air flow.. The PCM uses this signal to calculate fuel requirements.. 'Sometimes' the wire/s get coated with dirt/debris that 'insulates' the wire and throws of the signal to the PCM.. Remove the MAF and look into the bore, you'll see the wire/s on the inlet side.. VERY CAREFULLY spray clean them.. Disconnect the battery to clear the code/s after the cleaning, or clear them with a scanner/reader, and drive it for a few days until the diagnostic monitors complete.. If the CEL doesn't return, then the cause was the MAF...

RE: O2 Sensors?
 

Thanks ill try it its been real cold here today so maybe that has something to do with it to.

RE: O2 Sensors?
 

another question to confirm spray the throttle body cleaner in the tube on the maf or where the wires plug in to the maf?

RE: O2 Sensors?
 

You can clean it in 2 ways..

Pull the sensor out of the intake/sensor 'body' (but requires a torx bit,) or, you should be able to look into the intake duct from the air cleaner lid.. You'll see the 'nose' of the MAF hanging into the intake stream.. There will be 2 very small 'diode' looking wires stretched across the plastic nose.. These are what you want to clean..

Here's a pic of what a dirty one looks like... Not your exact application, but similar..


[IMG]local://upfiles/6756/7B1C2A015B4F4A3E9A2CDD118BC32D73.jpg[/IMG]

RE: O2 Sensors?
 

Whats the mileage on your explorer?

RE: O2 Sensors?
 

92,ooo miles on it i did it today so well see what happens. I cleared the codes i drove about 150miles tooday so far so good i hope

RE: O2 Sensors?
 

So were the wires on MAF dirty?

RE: O2 Sensors?
 

yes that took care of the problem. Thanks alot

RE: O2 Sensors?
 

Im having the same problem with our explorer 2000 4.0 it has 4 o2 sensors When the code reads bank 1 lean is that the 2 sensors in front of the cat. or is the driver side 2 which ones do i replace?

If its the 2 before the cats. how do you get to the electrical plug on the passenger side.