gamefreakgc
Elite Member
You can replace the rear/downstream sensor if you want, but the only reason why you would need to is if it throws a P0420 code or another code specific to the rear. It's the front sensor that controls your fuel injection.
P0172 code
- Thread starter Dezerts10
- Start date
You can replace the rear/downstream sensor if you want, but the only reason why you would need to is if it throws a P0420 code or another code specific to the rear. It's the front sensor that controls your fuel injection.
i ordered the upstream 234-4162 sensor off amazon. Guess ill try to make some time during the coming week to replace it and see what happens.
I might order the down stream sensor next pay check just because the truck has 206K miles on it and doubt it was ever changed.
gamefreakgc
Elite Member
I'm in the same boat, 220k and looks to be the original downstream sensor. Until it tells me I need to replace it, I'll just be leaving it alone though. It does very little except for telling you that your cat has failed.
4runnerfevr
New member
Just went out and bought a spark follower and installed it on the last o2 sensor, it's been a month and haven't had a cell. On my 4runner.
So looking for opinions on what to tackle next to try to get the p0172 from coming back.
On my ultraguage it has an open loop / closed loop features that I read has to do with air / fuel ration and the emissions system. It is open loop when warming up or under 100% throttle, and t goes back to closed loop after warm up and regular driving.
I have no pending codes and like mentioned before the CEL only comes on randomly and has come on the last three or four times under pretty significantly different conditions.
What should I check or replace next?
Thanks
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On my ultraguage it has an open loop / closed loop features that I read has to do with air / fuel ration and the emissions system. It is open loop when warming up or under 100% throttle, and t goes back to closed loop after warm up and regular driving.
I have no pending codes and like mentioned before the CEL only comes on randomly and has come on the last three or four times under pretty significantly different conditions.
What should I check or replace next?
Thanks
Sent from my iPhone using Tapatalk
gamefreakgc
Elite Member
Does it have a way to view short-term fuel trims? If yes, what are they at when iding with a warm engine in closed loop? If they are high, you have a vacuum leak somewhere.
<iframe width="800" height="500" src="https://www.youtube.com/embed/9CPqbaSgcok" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
Can you please elaborate on what maintenance items you've done so far?
I would do these items in this order:
Clean / replace air filter and MAF
Pull spark plugs and inspect and replace (cheap and might as well)
Check resistance of coil packs and wires (pretty much do this at the same time of the plugs) per FSM
check resistance of throttle position sensor per FSM
check for vacuum leaks (and replace hoses or just go ahead and replace them if they've never been done)
check resistance of injectors per FSM
(i'm excluding the 02 sensor that you said you replaced)
after that if you have still have the code post back.
I would do these items in this order:
Clean / replace air filter and MAF
Pull spark plugs and inspect and replace (cheap and might as well)
Check resistance of coil packs and wires (pretty much do this at the same time of the plugs) per FSM
check resistance of throttle position sensor per FSM
check for vacuum leaks (and replace hoses or just go ahead and replace them if they've never been done)
check resistance of injectors per FSM
(i'm excluding the 02 sensor that you said you replaced)
after that if you have still have the code post back.
gamefreakgc
Elite Member
If the code is not affecting the driving and was off for that long, pull the EFI fuse under the hood and replace it after 15 seconds or so. Will clear the code and hopefully you'll get another 1500 miles of code-free driving. I think either your engine either loves to foul sensors or you've got a wiring or ECU issue.
I had a 1991 Toyota that would randomly throw a lean code. I replaced so many things on it, full tune up etc. and it never went away. I just learned to live with it (had absolutely no affect on drivability or gas mileage) and would pull the EFI fuse every time it came back. Put another 50,000 miles on it that way with no issues.
Since you are running too rich it wouldn't surprise me if you have a throttle position sensor that is off or an injector that isn't working properly giving you too much fuel.
In response to a question you posted earlier:
10-1 (extremely rich)
12-1 (rich)
16-1 (lean)
you should expect to be running a bit lean when stopped since there isn't any load on the engine for the most part.
In response to a question you posted earlier:
10-1 (extremely rich)
12-1 (rich)
16-1 (lean)
you should expect to be running a bit lean when stopped since there isn't any load on the engine for the most part.
Hasn’t come on lately, but I haven’t been driving it much either. I don’t think I fixed it just hasn’t come back
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