Why does my check engine light keep coming on?

Question

The cat converter was stolen from my 2000 4Runner which was replaced. I have unplug the battery but the check engine light keeps coming back. O2 sensors were changed 6 months ago.

Answer 1

Better take that thing to a mechanic and have him check the engine.

Answer 2

O2 Sensor? Probably NOT the problem.
People like to blame the O2 sensor for the problem because that's where the computer fault appears.
However, nine times out of ten, it's not faulty. It is simply reading a condition in the engine that is causing it to send a signal to the computer that there is a fault in the exhaust emissions mixture.

Before you yank the O2 sensor and replace it, check the basics first. Otherwise, you could have wasted time and money on the result, not the cause.

There are many components that work together in the engine to maintain optimal engine performance and economy.
A service engine soon, or check engine light indicates that there is a sensor that is reading a condition that is "out of range".
Simply resetting the light does not solve the initial cause of the problem.
Replacing a number of parts trying to troubleshoot the problem in the hopes of getting the light to stay off is a tremendous waste of time and money.
The simplest, and most economical way to alleviate your issue, is to have an engine diagnostic done by a reputable shop to determine what caused the computer to signal you to begin with. Just reading the computer codes may not find the "cause".

Answer 3

I had the same problem, my check engine light would come on for a few days and turn off. The computer in your vehicle still memorizes the code which indicates the issue with your vehicle. Based on the year, it may be your Catalitic converter. Check engine light has to do with emissions, but it could be the Oxygen sensor as well. It may be something minor like the gas cap, best thing is to have it checked by a factory trained technician. O2 sensor you can expect to pay a few hundred dollars. A Cat. Converter is more expensive, the part itself will run under 100 dollars, most places will try to rip you off. You can expect a good honest place to have the part plus labor for under $300.00. Dont go to the dealership, it will run you are 1K which isnt fun.

Answer 4

The check engine light has a specific message for you: check the engine.

Even though you've changed a sensor and tried to unplug the power to the light, the check engine light is there to alert you to the fact that there's something unusual under the hood.

It could be as simple as low coolant or oil level, or complex as serious mechanical repair is needed. Either way, have a mechanic look at the codes it's putting out to determine the problem.

Answer 5

Could be something as simple as not tightening the gas cap enough when you fill up. Read your owner's manual -- most vehicles have a pressurized gas cap that you're supposed to turn until it clicks three times to work properly. If that's not it, the only way to tell is to take your 4Runner in to the shop and have them check the error code. The list of things it could be goes on and on.

Answer 6

Its possible that its on because the check like come on after a certain amt of mileage. I know that my check engine light comes on every 40,000 miles and shuts back off ever 40,000 miles. To be safe, i'd take it in for a check though.

Answer 7

Check the quality of the converter. Less than quality ones can bring the light back on.

Answer 8

You can buy a OBD code reader fairly cheap, and see for yourself, instead of paying a dealer to check & recheck for you. Some of the code readers can clear the check engine light off, too. Try Ebay

Answer 9

You need to have the engine checked

Answer 10

You need to have the 'codes read' to find out what's happening. It could be another sensor and have nothing to do with the exhaust.