It seems like the topic of oxygen sensors has been beat to death on these forums but I have yet to find an answer that works for me so I’m asking the forum, thanx in advance. I have 1999 ram v10, California edition. Cat has two in puts that go to one output. Out put is a 4” straight pipe. It has 4 o2 sensors. I looked it up and it should have two up and two downstream sensors. Can somebody clarify for me....do the up and downstream sensors have different plugs? They are similar but one has a notch a little off center. It’s looking to me like there’s 3 upstream and one down stream o2 sensors? Is this correct? And also, do I have to give the sensors time to reset or should it be running good right away? Hope this makes sense. Thank you all, Lynn

 

Look at the sensors you have, I think the differences are the connector, and how it's keyed, and the length of the pigtail.

You *can* just put the new sensors in, and call it a day, and the PCM will eventually re-learn them, however, I recommend resetting the PCM, and let it start from scratch. It'll learn much more quickly that way.

I can't find an accurate diagram of the exhaust, including sensors, with a quick search though.... Unfortunately, the service manual doesn't seem to have anything either.

 

Thank you your reply. 3 of the plugs are one way and the last one has the offset notches which I think means it’s downstream? I believe it’s left side manifold, right side and in the cat have one kind of plug and the one after the cat has a different plug. So I’m guessing it has 3 upstream and 1 downstream sensor. I just thought they were balanced for some reason. Resetting the PCM I just disconnect the battery for 20 mins, correct or do I have to drain the battery all the way? Thanx again

 

Yeah, just disconnect the battery, turn on the headlights, turn off the headlights, reconnect battery. When you go to start it up, turn the key to 'on' (not start) count to ten, then start the truck. (don't touch anything) it will quickly re-learn idle.

Idea here is to give the PCM adequate time to re-learn 'zero values' for the various sensors.

 

Ok, so I hooked up my obdII meter to the truck and I swear it says I have 5 oxygen sensors. Bank 1 sensors 1, 2, and, 3 and bank 2 sensors 1 and 2. Is this correct? Smh! Thanks, Lynn

 

On the california models, I just don't know. If it were me, I would just replace the three "front" O2 sensors, and call it a day. The rest are just to monitor the cats anyway. If you aren't getting codes for 'em, don't worry about 'em.

 

I’m trying to get my mpg back, plus pass smog, I passed emissions but not the monitors, anyways how important is a fully functioning o2 sensor system in terms of miles per gallon? It’s a v10 so it’s bad enough as it is, lol. It was 7.9 when I bought it and I had it up to 12.3 when it started giving me issues. I just replaced the fuel pump and o2 sensors at the same time and these are the readings I’m getting after starting it twice. Thanks folks

This is showing 5 o2 sensors, right?

Live data

Live data

Live data

Live data

 

What brand O2 sensors did you put in?

The numbers look ok. I just ignore the fuel trims of the rear O2's. They just monitor the cat anyway.

It may show a third sensor in there, but, that does not necessarily imply there IS one.... So far as I know, you should only have four...... But, again, cali emissions, and they do things their own way......

 

What about the open loop?

 

Certain things have to happen before the PCM will drop into closed loop, engine temp, X amount of time has to pass, and it needs to see the sensors switching properly. Until all those conditions are met, the PCM will stay in open loop. Under normal circumstances, once engine temp gets above like 100 degrees or so, it *should* go closed loop. If it's not, then something is missing from the equation. Since one side IS in closed loop, and the other side is not, they only thing they DON'T have in common, is O2 sensors......