code: oxygen sensor


  #1  
Old 05-01-22, 04:09 PM
sgull's Avatar
Member
Thread Starter
Join Date: Nov 2007
Location: AK
Posts: 2,682
Received 11 Upvotes on 10 Posts
code: oxygen sensor

The check engine light comes on periodically. Checked with a code reader and it indicates oxygen sensor. There are apparently two of them in different locations on my 98 Ranger. It's kinda weird because the check engine light comes on at rather random intervals, comes for several days or a week or two, then just disappears again for another several days or a week or two. No rhyme or reason it seems. Apparently one of these oxygen sensors is gradually failing maybe? Is this at all typical behavior?

My brother-in-law said sometimes it may be that simply the air cleaner (air filter) that needs replacing? Does that sound at all correct or feasible?

What's the worse that can happen if I just kinda keep ignoring it or let it go, if indeed an oxygen sensor does need to be replaced? Bad gas mileage?
 
  #2  
Old 05-01-22, 05:12 PM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Posts: 27,061
Received 1,910 Upvotes on 1,716 Posts
OBD codes are clues. No code is going to tell you with 100% certainly that one device (such as an oxygen sensor) is the problem, or that replacing it will fix the problem. So there is really no such thing as a code that says "oxygen sensor". That code probably lists oxygen sensor as ONE of the things it could be.

For example... PO134 causes could be:

A faulty O2 sensor, a faulty heater circuit, frayed or broken wiring, poor connection at the O2 connector, a vacuum leak, an exhaust leak, a faulty ECM, and probably a few other obscure things.

You can blindly replace parts, but its no guarantee it will fix the problem. Yes, your mileage could be affected (minimal) or your car could produce more pollutants than it should.

Once upon a time, I had oxygen sensors on my F150 that were malfunctioning. They appeared dead at idle. (No oscillating voltage shown on a live scan) But on the highway they appeared to work as they should (voltage oscillated as it should, like a wave, from .1V to .9V and back again) Along with other related codes, it ended up being a vacuum leak on the intake manifold, along with leaking isolator bolts. There was nothing wrong with the oxygen sensors. The reason they appeared dead was that due to the vacuum leak, there was more oxygen in the exhaust at idle than the mass airflow sensor said there should be, which caused caused ECM to throw a code.

Just an example to show that OBD codes are simply clues. And I doubt the air filter is any part of the solution. But if it's got 15,000 miles on it it's a good bet it should be replaced anyway.
 
sgull voted this post useful.
  #3  
Old 05-01-22, 05:26 PM
sgull's Avatar
Member
Thread Starter
Join Date: Nov 2007
Location: AK
Posts: 2,682
Received 11 Upvotes on 10 Posts
XSleeper thanks for that helpful info, much appreciated...
 
  #4  
Old 05-01-22, 10:34 PM
Marq1's Avatar
Member
Join Date: Sep 2016
Location: USA MI
Posts: 9,745
Received 1,210 Upvotes on 1,098 Posts
Typ there are 2 O2 sensors one pre and one post of the catalytic converter. All they do is compare the oxygen content in the exhaust to determine how well the catalyst is working. Get out of the range and the light comes on. Many things effect it's performance, catalytic convertor, vacuum leaks, EGR valve, etc etc.

We've got a Malibu with the light, it was found that the catalyst was replaced at some point (purchased used) and is not operating 100% efficiently. Even the shop balked at the $1200 cost to replace, for as little as it gets driven we'll live with the light, car runs fine.
 
sgull voted this post useful.
  #5  
Old 05-02-22, 06:51 AM
sgull's Avatar
Member
Thread Starter
Join Date: Nov 2007
Location: AK
Posts: 2,682
Received 11 Upvotes on 10 Posts
there are 2 O2 sensors one pre and one post of the catalytic converter. All they do is compare the oxygen content in the exhaust to determine how well the catalyst is working. Get out of the range and the light comes on. Many things effect it's performance, catalytic convertor, vacuum leaks, EGR valve, etc etc.
When my check engine light started coming on as I've described, (some six months ago), I borrowed my neighbor's code reader which indicated the code (I can't recall the code now) that indicates an O2 sensor-related issue. I assumed then (probably wrong) that most likely my O2 sensor needed replacement. Had a reputable shop check with their more sophisticated code reader, and I believe I recall the mechanic told me it was the post catalytic convertor sensor "throwing the code" as they say. I asked at that time how much they'd charge to replace that sensor and it wasn't cheap, but I am, and the car (actually a truck, a Ranger) still ran and still runs fine, so I held off on doing anything about it. Also at that time the vehicle was at the shop for a separate issue and so we didn't focus much more discussion about other possible causes for the code. I might go ahead now and see whether they can further troubleshoot and perhaps pinpoint the cause and go from there to do what it takes to fix the issue.
 
  #6  
Old 05-02-22, 09:00 AM
Marq1's Avatar
Member
Join Date: Sep 2016
Location: USA MI
Posts: 9,745
Received 1,210 Upvotes on 1,098 Posts
most likely my O2 sensor needed replacement.
That is a possibility also.
 
  #7  
Old 05-02-22, 12:24 PM
sgull's Avatar
Member
Thread Starter
Join Date: Nov 2007
Location: AK
Posts: 2,682
Received 11 Upvotes on 10 Posts
And, strangest behavior it seems, just today as I was driving around, the check engine light turned off by itself. And based on the recent past I can probably count on it remaining off for a week maybe two and then re-appearing again, and with the same code being indicated with a code reader.
 
  #8  
Old 05-03-22, 07:05 PM
A
Member
Join Date: Aug 2015
Location: USA
Posts: 1,054
Upvotes: 0
Received 113 Upvotes on 98 Posts
should still have a code even if the light went off sounds like it is probably a bad o2 sensor to me usually heater circuit faults do not go away, but if the computer does not detect a fault after 2 drive cycles it will often shut off the engine light but the code would still be stored in memory. and since a drive cycle can be rather short on short trips it may not always detect a fault.
 
sgull voted this post useful.
  #9  
Old 05-03-22, 08:58 PM
sgull's Avatar
Member
Thread Starter
Join Date: Nov 2007
Location: AK
Posts: 2,682
Received 11 Upvotes on 10 Posts
usually heater circuit faults do not go away
Forgive my ignorance but just asking... "heater circuit" faults have something to do with oxygen sensor(s) apparently? Briefly explain if you can on that please. Thanks!
 
  #10  
Old 05-04-22, 05:05 AM
the_tow_guy's Avatar
Group Moderator
Join Date: Feb 2001
Location: SW Fla USA
Posts: 12,237
Received 250 Upvotes on 202 Posts
Some O2 sensors have heaters in them, something to do with how they operate on cold starts.

https://www.ericthecarguy.com/o2-sensor-heaters/
 
sgull voted this post useful.
  #11  
Old 05-04-22, 06:13 AM
ukrbyk's Avatar
Member
Join Date: Mar 2010
Location: USA/ Pacific NW
Posts: 3,665
Received 62 Upvotes on 53 Posts
OK, error code per se always indicates, which sensor it is, upstream or downstream, accordingly, pre cat or post cat. On V-engines, it will also indicate, which bank it is, 1 or 2. That, pretty much, narrows it down to a specific sensor.
Intermittent O2 code normlaly will point towards not bad sensor but, bad contact. Bad wire, loose plug, etc. On v-engines, one simply swaps sensors left to right, just like plug or ignition pack, to see, if code follows the side change. On inline 4 banger, you start with unplugging the sensor and cleaning contacts, checking for any damage, lubricating with dielectric grease and plugging it back.
Such things should be done pretty much as soon as CEL come sup. Or, you end with posts like #5 here, no offense. Don't remember, I think it was, I think, guy said, etc.
Also, code should be stored in ECU memory, under stored codes.
For Ranger, O2 sensors are not expensive and easy to change. All you need is good O2 socket and lots of penetrating oil;.
 
sgull voted this post useful.
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: