Thank you both. It has been SO long since the Jeep has given any issues that I forgot O'Reilly and others read the code for you. Thanks for the tip and also thanks for the OBD reader - buying something similar, very handy! Out of town this weekend but bought a Wix oil filter and NGK spark plugs as recommended here. All gets replaced this coming week and hoping it isn't a major issue. Will update. :)

Cheers!

PS: Wonder if any of you'll watch the show Wheeler Dealers (its on YouTube). Great stuff.

Any time you have a check engine light, the first thing you should do is read the code. These other things could be red herrings that have nothing to do with why the CEL came on. This thread is now up to three pages of discussion of filters and spark plugs without any clear evidence either one has anything to do with your CEL.

If I were you, I'd take it to O'Reilladvanceautozone today, get the code read and write it down. Then come back and post it here.

Then, if you're going to own a Jeep, you really ought to invest in your own code reader. If you have an Android phone, you can use an inexpensive bluetooth OBDII adapter like the one linked above, along with Torque from the app store. Torque Lite will read codes, but I would suggest shelling out the $6 for Torque Pro, which has a lot more features that come in handy. Torque on an Android phone for less than $30 overall will do everything a $200 scan tool will do and more.

If you have an iPhone, you'll need a wifi OBDII adapter instead, and you'll need to get the DashCommand app instead of Torque. They do the same thing as the Android setup.

One warning: The cheap Chinese or Korean bluetooth adapters usually work fine, but DO NOT install any software that comes on a CD with those adapters. Those manufacturers download cracked copies of their software from warez sites instead of paying for licenses, and they often get copies that are infected with malware.

He's gonna get it checked Monday. And those code readers aren't always needed. I don't own one.i go to advance and done.

These 3 pages are to help him keep his jeep longer and to steer him from using inferior products.

Sure, you can live without it. But when it's so cheap to set up a phone with a reader on it, it's kind of silly not to, especially on a vehicle that's starting to show its age. I have actually pulled over with a CEL miles from the nearest parts store in rural Arkansas, read it with my phone, checked it on the internet with my phone, cleared it with my phone and driven on my way confident that it wasn't a serious issue. I have read codes in my garage, then walked inside and ordered the parts I needed rather than having to limp down to O'Reilladvanceautozone.

Yeah, I could live without it. But why would I want to?

And steering him toward better products was great advice. It just seemed strange to tell him to troubleshoot his CEL by changing his filter, when changing his filter won't tell him what code the computer is throwing and wouldn't be very likely to clear the code or fix whatever caused it.

Lol, of course changing the filter was not the real troubleshooting. Just getting him away from using inferior product. As for the reader.i went through three that never worked right, that's actually why I'm against it. All were recommended here. Funny thing. They were ask the same Chinese crap with different name

Yeah, get yourself an OBDII reader. Sure, you can run to AutoZone anytime but having your own is simply more convenient. I also like being able to see engine stats in a digital format rather than the gauge. You can read intake air temp, calculated engine load, throttle position, etc.


I'm not one for snake oils, but someone on here recommended some stuff called Restore with CSL a while back. Tried everything else (short of a rebuild) when I noticed a slight drop in oil pressure at 185,000 miles... That stuff brought it right back up, quieted the valvetrain, and brought back some compression. I had poor compression in my #2 cylinder and after using that stuff all of my cylinders are now within 5psi of each other. I haven't used it again since March and the engine's still running great.


Like I said, I'd never recommend another additive but I'm truly impressed by the definitive before-and-after compression tests.

Just got done with some work on the Jeep. I got the code scanned at O'Reilly. The code is: P0138 - Heated Oxygen Sensor (Bank 1, Sensor 2) Circuit High Voltage. I had the same code about 3 years back and my friend had cleared it then.

I haven't gotten to changing the spark plugs yet. I will this weekend. I changed the oil (Castrol Edge full syn, 5W-30) and put a Wix 51085 oil filter. Replaced the air filter. I also replaced the oil pressure sender - the past 5 years, every winter at cold temps, the check gauge light would randomly come on and the oil pressure gauge would be 0 all the time. When the weather improves, oil pressure gauge comes back to normal by itself. http://www.oreillyauto.com/site/c/de...r%21s%21switch

After the oil, oil filter and oil sender change, when I turned on the engine, the engine check light did not come on any more and has not since I drove back home (I had replaced the air filter prior and the light was still on after that step). The oil pressure gauge is still showing similar pressure as before. At idle it is 10 PSI, on highway about 2000 RPM, it is around 20-22 PSI. The engine is running smooth. The oil that was taken out was still good and about 5.5 quarts came out. It was Castrol Edge syn 10W-30 that I changed at 212,980 miles. Jeep now has 214,230.

I am wondering if it is the oil pump.

Again, thank you all for your help and recommendations!

4.0 check engine light came on
 

If your pressures are that low I would step up to a 5w-40 or 10w-40. It will help with the pressures. The check engine code could be a dying o2 sensor.