replacing o2 sensor
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battery1882
New member
I just went through this too.
It was reading high CO. I replaced the rear o2 and drove it about 2 tanks. No need for unplugging the power.
You do need to drive it accroding to cycle explained as follows :
http://www.toyotapart.com/READINESS_...T-EG02-003.pdf
It was reading high CO. I replaced the rear o2 and drove it about 2 tanks. No need for unplugging the power.
You do need to drive it accroding to cycle explained as follows :
http://www.toyotapart.com/READINESS_...T-EG02-003.pdf
fourfive
Senior Member
You can unplug the battery or use a scan tool if you want to quickly clear the check engine light but it will reset on it's own if the issue is truly fixed. After changing my rear O2 sensor the cel light cleared on its own after driving a few hundred miles.
If the O2 sensor fixes the issue but it states it is "not ready" for emissions testing, here is the link to the 3rd gen drive cycles. I had to follow the drive cycle instructions EXACTLY for my 4runner to read "ready".
3rd gen 4runner readiness drive cycle
If you don't have a scan tool or scan gauge, I would recommend getting one so you can check to see when your 4runner is "ready" for testing. You can get a cheap one off amazon for under $20.
TheDurk
Elite Member
Did you not have a CEL before? Did your readiness monitors show READY before? If yes to both, you should do nothing and just go back and see if it improved on the sniffer test.
If you don't know the readiness status before, then you should check them. Any reader or scanner will do it. If not ready, then you need the drive cycle. If ready, just go retest.
If you unplug the battery, it will not throw codes unless something is wrong. It WILL reset all your monitors to NOT READY and you will need to do the drive cycles to get them to READY.
Thanks for the info. No I didn't have a check engine light. I don't think it was throwing any codes either. From what I read I thought it was the 02sensor. But I didn't want to guess and just throw money at it so I got it looked at and they said it was the 02 sensor and wanted to charge me 500 bucks to fix it. So I took it back and did it my self, super easy. Now I just need to test for codes. Thanks again
TheDurk
Elite Member
In that case, I'd just take it back for a re-test as she stands. Check the readiness monitors if you have a scanner available for peace of mind, or just go.
TheDurk
Elite Member
Cool. I didn't think the Cali smognazis would pass you with a CAT NOT READY. Sorry if I mislead you on that. NJ would have dinged you, but NJ doesn't use sniffers on OBDII cars.