View Full Version : Oxygen Sensors
07-12-2007, 10:34 PM
Hey guys!!! You know... I consider myself to be a pretty literate when it comes to mechanics. I never did understand what happens when one's oxygen sensors go bad. I know they aid the ECU in running the engine efficiently. I guess my question is; is it bad to run on bad oxygen sensors? Or will it just decrease one's fuel mileage and efficiency? I ask because my check engine light came on today and the code says it's my oxygen sensors. Yes, I will replace them as soon as I have the funds, but would it be bad to run the trail this weekend with bad oxygen sensors? Thanks!!
07-12-2007, 11:04 PM
The ECU uses the O2 sensors to keep the engine running at the optimum mixture. If the sensor goes bad, the ECU will notice, trip a check engine light, and drop into a default/failsafe open loop mode, where it uses known safe values to calculate the amount of fuel to inject. This usually means that you'll run slightly rich when the oxygen sensors aren't working.
OBDII (1996+) vehicles typically have at two sets. The first before the catalytic converter, sometimes one per engine bank on a V engine, and the second after the converter(s). The first is used by the ECU to keep the engine at the correct mixture. The second one is only used to make sure that the first sensor and the catalytic converter are working, so it's even less of a deal than the first if it goes out.
I wouldn't worry about the errors. I drove my Land Cruiser for a couple of thousand miles before I found out that the previous owner pulled the check engine light and I had bad oxygen sensors the whole time. But that was my fault for not checking it when I bought the LC.
07-13-2007, 12:03 AM
Right on!!! Thanks for the input. I'm not too worried about it at the moment. Although I will replace them ASAP.
07-13-2007, 01:09 AM
Those are easy to change, BTW. I had one go out on me recently and I swapped it in about 15 minutes, and in the dark. Part found at local parts store, but wasn't too cheap.
07-13-2007, 02:54 AM
Yeah, I got my price from Autozone. They have them for $51.99 each. I didn't think they would be that much. Oh well, they should be replaced anyway.
07-13-2007, 05:56 PM
This is why I love hading a dad in the auto parts business ;)
07-13-2007, 06:19 PM
FWIW, this came up in Toyota circles before and I would imagine it would be true of most all cars. But sparkplugs.com sells O2 sensors and they are pretty inexpensive. For example, the NGK O2 sensor for my truck is $39 and is supposedly a direct fit. They also sell the Denso for $68 (so it is probably identical to stock, which is Denso and $100 from the dealer). I'm planning on buying one to see, but my O2 sensor is still good.
07-13-2007, 08:30 PM
Awesome!!! Thanks for the links. The check engine light for the sensors only comes on when I disconnect the battery and then reconnect it. I think when the battery is reconnected, the computer resets itself and sends out it's codes that have been erased. Last time I disconnected the battery, I took the troop to Autozone and got the same codes. It's weird that I can have the codes erased and then they don't come back on. I would think that if it was a continual problem, the check engine light would come back on.
07-14-2007, 12:33 AM
It's not unusual the see the check engine light come and go as O2 sensors reach the end of their useful life. Their response time gradually becomes slower and slower until they're right on the threshold of triggering a check engine light, so sometimes the ECU detects an error, other times it doesn't.
07-14-2007, 04:33 PM
But sparkplugs.com sells O2 sensors and they are pretty inexpensive.
$36.75 for an "OE identical" O2 sensensor?:punk03: Nice find Dave!
07-14-2007, 04:44 PM
Usually you will see a significant drop in mpg when your O2 sensors go bad. And since most on this forum advocate for better use of our natural resources and lessening our impact on the planet:) ... it's best to change them ASAP. Also, when your engine runs too rich for too long, it will destroy your cats.
07-15-2007, 03:36 AM
Usually you will see a significant drop in mpg when your O2 sensors go bad. And since most on this forum advocate for better use of our natural resources and lessening our impact on the planet:) ... it's best to change them ASAP.
Not to mention the ***-raping your wallet will take... :(
07-15-2007, 06:18 PM
Ha ha ha... yeah, I will be replacing them this week. Failure of the oxygen sensors definately makes sense as to why I'm getting crappy gas mileage.
07-20-2007, 06:13 PM
Has anyone replaced the O2 sensors on a gen2 trooper. YEAH... pain in the *****!!!! Holy crap!!! It's so damn tight in there!! When I had the codes read, it looked like both the passenger pre-cat and post-cat sensors were bad. Something about low voltage output from them. So it took me the better half of 3 hours just to get to the pre-cat sensor replaced. I didn't bother with the post-cat sensor because it to is in a very awkward spot and would take another 2-3 hours of hell. On the post-cat sensor, it looks like both the male and female connectors have been corroding for a while. When I pulled them apart, there was a bunch of white crusty stuff that came out. So I think I'll try to find new connectors too before I tackle that sensor. The driver side sensors ar super easy to replace. So far, everything I've had to replace on this trooper has been a major pain!!!! Don't get me wrong, I still love it and wouldn't trade it, but it's a hard rig to work on.
gotta love the search function :) ! check engine light has been on for a while, turns out its the 02 sensor and the mass air flow (sensor, ?). had the dealer check it out today, no charge for the diagnostic but to get both replaced is $515, is this rediculous? i just put $1000 into the rig with parts and labor for my 90,000 mi scheduled maintenece...now this, ouch. i need to reread this thread however and looking to alternate part sources and the possiblity of installing thes myself apparently. thanks guys!
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