Is true you have to use oem sensors?....are there two?...I am in Massachusetts...I had check engine code p0420, changed catalytic converter(walker), last year, 10,000 miles ago muffler and rear pipe with walker stainless steel, converter and pipes were welded at muffler shop. Appreciate any info

 

Well, yes, they are better. NTK is the brand, I have them on my 5.9. Even Amazon has them. That said I have Bosch on my 5.2, been there about 8 years now no problems although some guys will make the sign of the cross at the mention of Bosch O2's. You should have one before, one after cat. These systems don't use O2 readings to adjust fuel or air, all it wants to see is a different reading out of the cat from the one ahead of cat. For that reason I only bought the NTK for the front and left the rear one.

 

Thanks for advice, really appreciate it. I noticed that the some NTK sensors can be used for both locations. Seeing that it is looking for simple reading is it possible.....instead of upper stream right part number and lower stream left part number

 

the sensor count depends on emissions setup on your truck, CA emissions had 2 upstream and 2 downstream sensors (and 2 precats which they monitored), standard setups had one cat and one of each sensor. the p0420 code is a cat efficiency code, this refers to the post cat sensor or the cat itself since all that one does is monitor the cat for emissions gases below a certain threshold. The pre-cat sensor is the important one since that is the one that runs the engine when it warms up, if your gas mileage drops without a code its likely a pre-cat o2 sensor going out.

yes OEM sensors are preferred



who told you this? they are DEAD WRONG the O2 sensor before the CAT is used to run the engine at an optimal efficiency once the engine is at operating temperature (its called closed loop operating). Just look at what happens to your gas mileage when the pre-cat sensor goes bad if you dont believe me.

 

Once again thanks for all the input, you got to love the forum. We are trying to help each other out and that is awesome.

 

from the mouths of babes ... PRE-CATALYST OXYGEN SENSOR

The pre-catalyst O2S sensor is located in the inlet end of the catalytic converter. It provides an input voltage to the PCM. By comparing the input from the pre-catalyst O2S sensor, with the input from the post catalyst oxygen sensor, the PCM calculates catalytic converter efficiency.

POST CATALYST OXYGEN SENSOR

The post catalyst heated oxygen sensor threads into the outlet end of the catalytic converter. The post catalyst heated oxygen sensor input is used to detect catalytic converter deterioration and fine tune the air fuel ratio. As the converter deteriorates, the input from this sensor begins to match the pre-catalyst sensor input except for a slight time delay. By comparing the inputs from both of these sensors, the PCM calculates catalytic converter efficiency.

When the catalytic converter efficiency drops below emission standards, the PCM stores a diagnostic trouble code and illuminates the Malfunction Indicator Lamp (MIL).

 

thank you for explaining what we already know about how the codes get set, the post cat sensors are there ONLY for emissions, the pre-cats are used for both running the engine in closed loop and as a reference to compare to the post sensors. take out (unplug) your pre-cat sensors and see what happens to your gas mileage if you don't believe me(hint: it will tank). If they aren't used for closed loop operation then nothing would happen.

 

You need to keep reading further down that section. The front O2 sensor monitors fuel mixture ratio in closed loop operation, and the PCM uses that info to try and maintain a 14.7:1 mixture ratio.

 

you know what's funny.... no body pays attention. I from the beginning said, use the factory NTK 02 for pre cat, after that nothing matters, who cares about the post 02, many guys with cat delete tubes just zip tie to frame.

 

And that would be good advice. It is the passing of misinformation that we object to. (O2 not used for fuel mixture.)