Check Engine Light came on.....code was O2 sensors.....replaced myself..... mechanic cleared codes.....Said I had to drive at least 100 miles for reset to register inspection with DMV......Drove nearly 550 miles.....said the computer still is not resetting unable to inspect. Now overdue! Is this a common problem?? What should i do to get computer to reset. Not showing codes anymore and no check engine light...but can't inspect!

These may be few possible reasons why the check engine light won't go away after replacing the O2 sensor in your 2000 Mitsubishi Eclipse V6

·The wrong O2 sensor was replaced or the O2 sensor is properly connected to the wiring harness(any signs of damage or corrosion).
·Sometimes, issues with the engine, such as misfires, vacuum leaks, or problems with the fuel system, can trigger the O2 sensor to report a problem. Ensure your engine is running smoothly and there are no other issues that could affect air/fuel ratios.
·The new O2 sensor is defective. If the O2 sensor is working properly, then the check engine light could be due to another problem with the exhaust system, such as a leak or a problem with the catalytic converter.
·Problem with the wiring to the O2 sensor. If the wiring to the O2 sensor is damaged or corroded, it can cause the sensor to malfunction and trigger the check engine light. To diagnose the exact cause of the problem, you will need to have the car scanned by a qualified mechanic. The mechanic will be able to read the trouble codes from the computer and use that information to pinpoint the problem.

I'm sorry you replaced the parts without testing first. Codes only give mechanics a suggested area to test, not which components to replace.
Since you replaced the O2 sensor for the first two codes, a mechanic will need to check to see if it is working by reading the data flow from the sensor with a scanner while the engine is warming up. The catalytic converter will also need to be tested to troubleshoot code 431.
Code 455 is for a leak in the evap system which is what vents the gas tank to the vapor canister. The system will need to be pressure checked for leaks and then repaired.
Keep in mind, once the repairs are made and the codes erased, the car will need to be driven at least 100 miles in various conditions before you re-test.

I guess I should start by saying that trouble codes do not instruct the mechanic to replace a component. Only to check it.
Code 31 is for a problem with the heater circuit for that O2 sensor. The sensor is not warming up fast enough to satisfy the engine computer. Since you have replaced the sensor, the actual problem could be in the wiring or the source of power for the heater built into the sensor.

CHECK ENGINE OIL PUMP

Why would a mechanic tell you to drive a vehicle
with an O2 Sensor Code, and why clear the code?

Plain stupid

PO153-O2 Sensor (Bank 2 Sensor 1) slow response

Just buy the sensor and replace yourself.

It is slow because it is worn out,most likely over
100,000 miles on it

Replace both front sensors ,if you have 2,the ones
closest to the engine

Can't tell you exactly what is wrong but the one thing you said is of concern...Map sensor should not be full of oil. If it is, I'd want to know why. In finding the reason for that, you may also find the reason why you are having a problem.
Jeep uses two kinds of engine crank venting. you either have a pcv valve or an orifice controlled system. If either are obstructed it can overpressure the crankcase and cause all kinds of problems.
Years of experience tells me this isn't something I can guess at and be 100% sure I have the right answer but based on what you said, I'd look there first!

there are no codes that say replace O2 sensors,or remove converter,Thats just somebody's guessing,When it says O2 sensor that tells the mechanic to look for trouble in that area,wiring or faulty readings,And there are four O2 sensors.

Well an engine vacuum leak can cause the P0171 code to come on and having an oil cap missing is a vacuum leak. The first response for this code is to replace the O2 sensor because that is what the code is for...bad O2 sensor reading. Now too much air from a vacuum leak can cause a lean condition in the exhaust. If they are going to replace the O2 sensor for free then let them..If you trust them to replace it. It is possible that the lean condition could have damaged the O2 sensor. You may find that after a few days of driving with the cap back on the check engine light might go back off. I do not think anaything would be permanently damaged as long as the oil level did not get too low and nothing got into the engine thru the open hole in the valve cover. Does the car seem to be running ok? No overheating, miss, ect.

Hi,first thing your cambelt and tensioner should have been replaced 13k miles ago,it would pay you to replace the water pump at the same time as they are known for impellor failure = cooling system fault=P2181 code,hope this helps.
Darren

There should be a reset switch that turns the light off. Some vehicles require a code scanner tool to reset the check engine light. On some Isuzu models you have to remove the instrument cluster and move a screw from one hole marked KSW to another hole with the same KSW marking (it may have tape over the second screw hole). Other Isuzu models may have a small switch on teh back of the instrument cluster or may have a different marking on the screw holes (some were marked wit the letter B on both holes). The O2 light usually comes on at 90,000 mile increments which is when Isuzu recommends changing it.