I have an 05, 5.7 hemi with 81,151 miles to be exact.. the check engine has been on and off for awhile,more on then off. i getting a code of 0420,is it safe and not hurting anything to drive? truck seems to run pretty good.. thanks guys in advance...i've been driving it for sometime now...

 

Your Catalytic Convertor is most likely the culprit...
A cat that is only 5% clogged could throw this code.
An old school way of fixing this is add a gallon of lacquer thinner to a 1/3 of a tank of gas and run it for 100mi or @ 2500 rpms for a 1/2 hour to clean the cat.

 

Also you can check and make sure there are no cracks in the exh manifolds and no broken manifold bolts that would allow fresh air to be sucked in the exh and go past the O2s

P0420 is the left side I believe

 

Will check that out weed.. so add a gallon of laquor thinner to about a quarter tank of fuel?do i need to run that out all at once or can just burn it off going back and fouth to work during the week

 

Do it before a hiway trip of 100 miles or so...
or let it rev in your driveway at 2500 for half an hour.

 

I've always wondered if you could burn it out. Like revving the engine while torching the cat cherry red. I wana say I heard about this with diesels.

 

Wont be going on any 100 mile plus trips anytime soon,so is it safe to rev the engine at 2500 rpm under no load for ahalf hour.. might go this route instead..

 

Just keep an eye on your gauges especially your temp.

 

Thanks mopar...

 

The P0420 code comes from the downstream O2 sensor. It means that it senses a catalytic system deficiency, and as stated above, it only takes a 5% drop in efficiency to cause that code. However, it can just be a faulty sensor. The sensors are relatively cheap and relatively easy to replace. I bought my daughter a 2000 4Runner in November of last year and the CEL came on when I was driving it home. The code was P0420. I tried resetting it a couple of times and it kept coming back. So, I ordered a sensor online and replaced it myself. 9 months later and the code has not come back.

Another indicator that it could be a bad CAT is bad mileage. Have you noticed a signficant drop in mileage along with the intermittent CEL's? If so, it's more likely to be a bad CAT and not a bad sensor. An exhaust leak in line anywhere in front of the sensor could also be a culprit.

So, in my opinion, experience, the logical order of things to look for when you get a P0420 is first check for exhaust leaks. If you find no leaks, try a new sensor and let it complete a drive cycle and see if the code comes back. If the code still comes back, you likely need a new CAT.