Jeep Liberty 2005 check engine light won't go out

I got a new-to-me Jeep Liberty 2005 in February. The check engine light came on after a few weeks. Our mechanic replaced the catalytic converter twice. After the second replacement it went out after we drove for a while, but after the second one it never went out. We are now using high-test gas (to prevent carbon buildup?), but that hasn’t worked either. I need to pass the emission test soon.

You need to find a real mechanic. I would suggest a good independent mechanic with a good reputation in your area. The CEL system is very weak when it come to pinpointing a particular problem on your vehicle. A real mechanic will use the code(s) generated along with experience and proper troubleshooting to find your fault. Simply reading a fault code and throwing parts at it will not turn off a check engine light.

Stop wasting your money on high test gas.

Regular gas and high test gas has the same amount of detergents in them.

The only difference between the two is the high test gas prevents pinging in engines with high compression.


You paid to have this problem fixed and it’s not fixed. What does this mechanic plan to do about that? Isn’t there a warranty on their work?

I agree with missileman. I support lion philosophically, but if this shop has replaced the cat converter twice they’re probably not capable of diagnosing the true cause. No sense going back again or you risk them throwing another part at the problem without knowing the cause… at your expense, of course.

I really think Liberty 50 should find a new mechanic as everyone here agrees.
To replace an expensive cat twice is just guessing and hoping to hit on a cure.
Maybe he’s just working his way from the back to the front???

Go to any chain parts store and they will read the codes for free. Then post the codes here so we can diagnose the problem.


Have the codes read as others have said.

It’s quite possible the problem is a faulty oxygen sensor. The sensor says the cat is bad, so the mechanic replaces the car. But the sensor itself can be faulty.