If a new 02 sensor was $100, I would change mine just for the peace of mind and hopefully for better gas mileage. But, I'm unusure about the right 02 sensor since I live in California. Some say that you can get away with the cheap one and others have said you need the California specific one. Does anyone know what the right answer is?

 

I wouldn't know that answer and I personally would not chance it because I don't remember the Smog Cert regulations in CA. I havent lived there since 1995.

Some have asked for my MPG update so here it is...I filled up yesterday evening because I have a training this weekend and my MPG was 18.27!! I get happy because that is about 5.9 MPG better than before the O2 sensor replacement. I was getting a CEL and am not saying that you will get improved MPG just by changing you O2 sensor. I am just fulfilling a request for my continued MPG numbers.

These numbers are a combination of stop and go highway traffic, city driving, and one extra 40 mile trip at regular highway speeds. Mind you, I am not very gentle on the throttle so I am certain that I could get 20+ if I took it easier.

 

Ok...I ran the mileage from the weekend and with one stop and go trip on Friday and a lot of freeway driving over the weekend and was able to get 21.20 MPG. Again, I step on it pretty hard so I know if i were to (read: could) change my driving habits I could probably get 23 MPG without breaking a sweat.

 

It is your O2 sensor I bet. You have the same situation I did about 6 months ago. I went from about 13.5 mpg to 17.2 after I replaced the o2. Before that I had done a full tune up (plugs, wires, filters cleaned MAF, throttle body cleaning, sea foam) which only added about .5 mpg.

Drop the bucks to replace the o2, follow the install write up that is a few post back in this thread and report back.

 

Did your truck throw a code or did you just replace the 02 sensor b/c of the mileage issue? Curious since I just did full-blown maintenance but was waiting for mpg numbers before I did the O2 sensor. I confirmed for all the Cali people out there, at least 99 and prior use the regular $100 02 sensor, nothing special.

 

Yes...My truck threw a P0171, P0130, P0133

 

Doublezero and Alpine, quick update:

Had my truck back for the last week after a major service, including BG flush, tranny flush, plugs, fuel filter, etc. My mileage has only gone down on one fillup from 15 to 14. My truck hasn't thrown a code but I have to think it's the 02 sensor. I will change it in the next couple of weeks and hopefully, this will help bring it up to 18 mpg...

 

Yeah doublezero and ebelen-
I just dropped 700 bucks for new 265/75/16 bfg AT KO's since mine were bald. what a difference. anyways, i havent bought my 02 sensor yet, cause we just got snow and that fueled my reason to grab the tires first. I will let you know when i order it, and get it in.

 

I got code P0171 on friday after I cleaned the TB or IACV. I cleared the code and cleaned the MAF sensor and also cleaned my K&N filter (I know I know) I did re oil lightly and wiped off any extra oil. I started the truck up and it ran fine at first no CEL. I shut it down and let it sit for about 2 hours then I started it back up, at idle it through the CEL again. I believe that it could now be the O2 sensor though I still getting around 17-19 mpg.

Does anyone have any other ideas? Should I trouble shoot the MAF sensor?

 

Not sure on that one. If it failed again so quickly I would start with the MAF. You got any Pick-A-Part's (junk yard's) nearby?

My CEL came on after about 50 + miles of driving and I recall someone telling me that the O2 sensor took a while to throw a code.

 

Well I rechecked everything last night and reset the light. I drove today 70+ miles and it just came back on. I haven't had a chance to check the code. But reading what DoubleZero wrote then it maybe the O2 sensor.

I really hope not only because of the California specific O2 sensor being 209.99

 

I know the pain you are going through on that one. If its the P0171 only, I would search around and see if you can find a MAF from a wrecked 3rd gen to see if the MAF is your problem.

Mine was throwing three codes and others have said that a lone P0171 turned out to be a MAF.

 

I thought the same thing but my mechanic checked and my '99 uses the cheap 02 sensor. I also live in Cali so have someone check for you to be sure.

 

You can also give your VIN to the dealer and have them cross reference the correct part for you.

 

Jamie,

Need your advice. I decided on not replacing the 02 sensor since my truck hasn't thrown a code. My mileage issue started with the lift and bigger tires so I'm assuming it's this. When I do the calculation on how much my speedo is off, it's fairly drastic. IIRC, it's about 10%. I went from 28" to 32" on the tire size and upsized to 16" wheels. I then added the tundra brake system so I figure I'm the devil when it comes to the mpg.

I've done all the maintenance so I'll just have to live with my mods. Would you swap out the 02 sensor without a code?

 

Depends on the mileage....if you had over 100k on it I would say yes in principle, but it is possible you are replacing a good sensor. Without an OBD II tool that allows you to look at the signal coming from the O2 sensor then I would just go by mileage. If you are in the 70-100k range it is up to you and less than 70k I would doubt that it has had enough cycles to degrade the sensor's performance (although I have seen some go bad at less than 60k, but that is rare).

 

I have access to an OBD II tool but I thought it didn't work w/o a code? Also, I'm almost at 100k but I'll try the OBD II reader first. Thanks.

 

When I say OBD tool I mean one that allows you to view the actual signal coming from the O2 sensor such as the Auterra (PDA based like the one in my signature) or various laptop based versions as well (as discussed a few times on the board, just search OBD II). A simple generic code reader won't help at all in this case.

 

Well I believe that my problem is the MAP sensor now, Because after 2 fill ups I'm staying pretty consistent on gas milage.

I'm sure of the O2 sensor was bad then my gas milage would go to ลลลล?

 

For those interested....mileage still hovering between 18.7 and 21.2. Well over 2K miles on new O2 sensor