Check Engine Light
Jeep Liberty Sport
VW Jetta

How do you reset a check engine light on a 2002 Jeep Liberty Sport 4x4 with a 3.7L engine?


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2015-07-16 19:31:07
2015-07-16 19:31:07

Question..... I was wondering if anyone could help with a problem my wife has been having with her 2003 Jeep Liberty Limited. The vehicle has 88K miles and runs well. About 2 months ago, the check engine light came on and wouldn't go off. My wife took it in for an early oil change and diagnostic. The oil change didn't solve the problem and the diagnostic showed nothing wrong. Then a few days later, the light went off. A few days later the light came back on again. She then brought the vehicle to a mechanic and, after diagnosing the vehicle for over 2 hours, decided that the gas cap needed to be replaced. The light went off. 2 days later, the light came back on again. Brought the vehicle back to the same mechanic who did a full oil change, tune-up and replaced the gas sensor. The light went off. That was yesterday. Today, the light came back on again. I refuse to bring it to another mechanic and have them "guess" at the problem, charge us an arm and a leg and wind up having the liht come back on a few days later. Any suggestions?

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Thanks to anyone who can assist..


It has to ba done with a scanner. Take it to a autozone or other parts store and they will read the codes

Don't waste your time at autozone. Pull the codes from the computer, match the code to the troubleshooting procedure, follow the procedure to find the source. Repair the source, light will go out if that was the only problem. There are "monitors" or self tests the computer runs the car through a drive cycle, if a problem occurs, it may not run all of the self tests until that problem is taken care. Therefore, another problem may exist. It is emission related. OR hook up a scanner that is capable of clearing codes, and hope that none are still active. Disconnecting the battery can create other headaches and will not likely solve your dilemma. Best bet is to contact the local snap-on dealer and have him refer you to a known good shop that specializes in this technology-he will know.

The " check engine light" is by far one of the most misunderstood technological advances by the public. This is an needed in-depth understanding for the public. It is a warning light that is illuminated when there is a problem affecting the EMISSION SYSTEM only. Emission system being the pollution control system. Don't get a hard on against it as it is a good thing once you understand it. One point that was brought up a a recent meeting of technicians was that the amount of hydrocarbons is greater when the gas cap is left off than when the engine is running. Hydrocarbons are part of pollution emitted as gasoline evaporates. Going a step farther, one facet of the emission system is the "Evaporative" portion. This is when the fumes from the gasoline are leaking from the system into the outside air. This is one part of the emission system that can trigger a check engine light. I would say that about 7% of the vehicles that have a check engine light are the result of a loose or inadequate gas cap. But understand that many scenarios are possible with the "check engine light" The vehicle's powertrain computer (note that some vehicles have 17 different computers) will run a series of self-tests. They will only run under certain criteria. And they can be vastly different from manufacturer to manufacturer. Some self-tests are not run until preceding ones have run successfully. So if there is a problem in one particular area that is preventing another self test from running, you can have a situation where one problem is fixed, but another still exists. If you fix a problem and drive the car through a drive cycle that sets the monitor (or self test) the light will go off as it passes that criteria that triggered it in the first place. After 1996, the auto industry went to a idea called OBD II (on board diagnostics). This was to get all the manufacturers onto a similar plane for troubleshooting and powertrain control. While they still differ vastly, many corrections and adaptations were made for technicians to better fix the check engine light problems. Prior to this there were so many different and poor troubleshooting data from a check engine light problem that resolving the problem was much more difficult. Many early warning light of this nature were set to illuminate based on mileage. An Oxygen sensor was one of the things that were meant to be replaced when that mileage was hit. This is much like many current "Change oil lights? that are set based on a pre-set mileage. BCLEAR.

BCLEAR - your answer in reference to the engine light coming on due to an emisions problem may be on target. My wife went to put gas in our 2002 Jeep Liberty and noticed that the gas cap was missing. She was concerned that an old friend that she is fuding with put sugar in the gas tank and stole the gas cap in the process. Shortly after fueling up the check engine light came on. Obviously I did some research on what sugar in the gas does and learned that most of the stories are urban legends because sugar does not disolve in gas. The engine light came on only after she drove the car without a gas cap. I will get a new one today and see if that clears out the code. Don

Best thing to do is remove the negative cable on the battery and let set over 15 to 20 min. Then reconnect and see if it went out some times its just a matter of resetting the computer for routine maintenance. Had light come on after fuel injection cleaning. Pulled negative terminal and the light has never come back on.

_ Comment: I find that everytime I fill my almost emtpy gas tank with gasoline containing 10% ethenol my check engine like comes on. Only after filling my almost empty gas tank again with gas not containing ethenol my check engine light goes out. (after half a tank of gas is burned.) You can read the content of the gasoline that you are purchasing usually on the pump. Most time it is in small lettering. I hope this is helpful it works for me. Try this first you won't waste alot of trips to the dealer and most dealers don't know this. I just descovered the pattern myself.

At about 90,000 miles, my check engine light came on as well. My mechanic ran diagnosis on it....I had cracks in my emissions tubing. After replacing the fix...the light went off.


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