I own a 2005 Jeep Wrangler Unlimited. (2 door, long wheel base) The jeep runs great, but the check engine light has been on for several years now. The mechanic says that his computer is showing that all the o2 sensors are bad. He says that all the o2 senors being bad is unlikely, but it's probably a computer issue instead. He's referred me to another mechanic that can fix the computer but it would be around $1200.

I don't want to pay $1200 just to the the light turned off. Any suggestions? Any other possible problems or fixes?

Thanks
Ryan

 

That 2005 Jeep Wrangler Unlimited is a TJ (or aka "LJ"); you'll get better responses from a TJ forum rather than the JK forum here (JK is 2008-2017).

That said, #1 it shouldn't cost $1200 to replace the O2 sensors and #2 the readings from the O2 sensors indicate the health of the catalytic converter.

Basically you need a new mechanic. If you are getting a CEL from each of two O2 sensors then that indicates you have at least one bad catalytic converter (IDK if the TJ has a so-called "pre-cat" but if so it may also be bad). The O32 sensors are routinely replaced along with the catalytic converters. On most vehicles this is a reasonable DIY job as long as you have a way to get rusted bolts out, but if you hire a pro it should cost no more than a few hundred bucks in labor plus parts. Nowhere near $1200.

Best to go to the TJ forum and ask the same question.

 

Another thing here...it is possible that all 4 are reading bad. The TJ was notorious for only liking factory sensors. Mine wasn't happy with the Bosch sensors. Back to Mopar and it was back to normal.

 

Thanks for your input. I'll find the TJ forum and ask as well.

 

How is it "showing" that all of them are bad? Did he pull different CEL codes for all 4 sensors? That doesn't necessarily mean they are bad. So I take it as he never properly diagnosed anything, and now suggests you fix your PCM for $1200. Find a different mechanic, that does proper diagnosis. With a proper diagnosis there is no "maybe" or "likely", but rather "certain" and "confirmed".

 

Can the o2 senors be removed and checked with a volt meter?

 

You'd want to test them with a scan tool while they are operating. A volt meter I guess can be used if the sensor is fixed rich or lean.

 

You could measure the voltage while they are operating: installed and with the Jeep running.

The way they work however is an O2 sensor is positioned on either side of a catalytic converter so two O2 sensors' data can be used to calculate the effectiveness of the catalytic converter. Most modern (OBD2 or later ... 1996+) auto ECUs are pretty sophisticated with how they do this analysis.

IOW getting a low reading on an O2 sensor is more than likely caused by a faulty cat than a defective sensor. Getting zero volts (that is 0.0 ... they are always well below 1V) would indicate a bad sensor which would also be indicated with an OBD2 code showing which specific O2 sensor has low voltage.

Just get an OBD2 code reader and stop trusting mechanics blindly. The ECU does a pretty good job of telling you specifically what the problem is, but you may have to do some interpretation since it really just gives data and not conclusions. So an O2 sensor code may not mean bad O2 sensor, it may mean among other things bad cat, malfunctioning fuel injector, ignition, etc. Many reasons, usually many codes, and a little bit of logic.

 

I have a 2007 Jeep Wrangler Unlimited X with about 186,000 miles. I thought I'd try a different place for its basic oil change/tire rotation, and about a week after that, the "check engine" light came on. I was told that perhaps I put some cheap gas in, paid for a little splash of the fuel cleaner for $7 something, and I was good to go for a little while. I'm traveling out of town, and the light returns. This time I'm told it's overdue for a tune up, and with a bad spark plug causing some issues too, so I had all of that done for about $400. A few more weeks, and bing! Light's back on, and I'm told it's the O2 sensor now for about $150. Light's off, light comes back on, and the code gives the O2 sensor code issue again. I'm reassured that it's not an emergency and I can drive out of town again, so on my return, I'm back again to see these folks for yet another Sunday. Meanwhile, the codes I'm getting are: P0430 for the O2 sensor, P0706 for the transmission ranger sensor, and then 2 more O2 sensor codes. I'm told that it would be about $500 for the catalytic converter because that's likely the issue, but I could go to a Midas or someplace for a less specific cat. conv. and it would be about half the cost, but again, there is no emergency. I decide to call up my usual car folks, and they say it will be more like $1200 and up! Said I actually have 3 converters so there's the problem,and again, no worries, I can travel as I need to, but at some point, it won't be efficient. The car rides relatively well, although at times it acts like it isn't going to start. Any suggestions? Thanks, thanks!!

 

Msgraciey, can't give you specific action, but can tell you of my own experience. I had just the P0430 code. Since I had over 200,000 miles, changed out all four O2 sensors. Did not fix the problem, but figured if I was going to replace the cat eventually, I'd put new sensors in anyway. Next swapped out the cat. Problem fixed. The cat is going to cost a lot more than $500 unless you buy some non-certified device that may or may not take care of your light. I'd stick with legit parts. If you don't want OEM (it's expensive), at least ensure that the manufacture is building to OEM specs: It will be 50 state legal, not 49 state legal. Anything less and you may just end up with another check engine light and chasing your tail further down the money hole.

You can find them for under $400, but here's the OEM part. Obviously, the $500 estimate was for something dubious, the $1200 bid was probably something that will actually fix your problem.

https://www.quadratec.com/products/57605_0000_07.htm