My check engine light is on,but my jeep runs fine.Anyone have any ideas??

Question

I have a 2001 Jeep Cherokee. Has a 4.0 liter 6 cyl.engine,2wd.The light has been on now for 4 days .I had an oil change and regular maint done on it 3 days ago with no change.It has 134,000 miles on engine.

Answer 1

CHeck your gas cap and make sure it's tightly on. When it is not, air gets into the tank and causes the light to go on. Good luck!

Answer 2

If the Check Engine light is flashing, there's a serious problem that will cause damage to your car shortly. Go get it fixed!

If the Check Engine light is on all the time, then it may or may not be serious.
[As I understand it, this light actually is designed to indicate that something is wrong with your pollution control, not your engine.]

The best way to definitively know is to query the car's computer using a special tool.

Dealers or mechanics will do this, usually for a diagnostic fee. Some parts stores may lend you a tool for free. A do-it-yourself mechanic may use a tool like AutoTap.

However, this often (but not always!) due to a leak somewhere in your fuel system. Allowing fuel or fuel vapours to leak into the outside world is considered an emissions problem, so the light goes on.
[Sensors detect how long it takes for vacuum applied to the fuel line to dies down. If it's reasonably fast, then there is a leak somewhere and the light goes on.]

Some common reasons I've heard for the Check Engine light are:

1. Gas cap: poor seal. A gas cap that isn't tight, or has worn out rubber gaskets can cause a fuel system leak. Once you fix it, it may take a couple of driving cycles for the computer to reset and turn off the light. Fix = cheap.

2. Gas tank pressure relief valve: rusted open. There's a valve on the gas tank to make sure that there isn't too much pressure built up. It can get rusted open. Fix = not cheap. The valve can be expensive. My friend was quoted CAD$450 (about USD$375) for the valve alone.

3. Fuel filter: not connected tightly. If you've just changed your fuel filter (you mentioned some 'regular maintenance' done recently), check the hose connections and make sure they are nice and tight. Fix = cheap.
[You might even go back to your garage and mention that the light has been on since the maintenance (not a lie) and see if they will diagnose it for you.]

4. Oxygen sensor: dirty/fouled and needs replacement. This is a sensor that is usually located under the engine on the start of the exhaust pipe (just after the manifold). Your Jeep may have a second sensor after the catalytic converter. It's like a spark plug and pretty easy to change if it isn't rusted into place. Fix = not that expensive. Oxygen sensor probably $50-150 depending on which sensor. You may need a more expensive or cheaper one depending on if it's the Classic or Limited model, etc.

5. Many other reasons. Small puncture in the fuel line. Cracks in rubber vacuum hoses. Etc.


Some people continue driving for days/months/years ignoring this light, as the engine itself may be unaffected. I wouldn't do this myself.

It's my recommendation that you should get it checked out and fixed so that you aren't driving with the Check Engine light on. One day you might get stranded on the highway, and that sucks more than getting your car fixed.



DISCLAIMER
I'm not a mechanic. I don't pretend to be an expert on this topic, so take this advice with a grain of salt.

Please note that I'm just recounting experiences I've heard for the Check Engine light. There are a multitude other reasons why this light might come on that I don't know about.

Answer 3

I agree with those who told you to run a free scan on it at AutoZone, Advance, or O'Reilly's. However, don't buy any parts that they recommend.

If the vehicle is running well, it may not be a problem and the light may go back off the next time you fill up. However, do be aware that on a larger engine it is possible for filters to clog so gradually that the driver is not really aware of the diminishing performance, which is why a diagnostic scan is always best.

The 4.0 jeep engine is good for more than 200,000 miles with regular oil and filter changes, so your vehicle still has plenty of life left --- take good care of it!

Answer 4

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RE:
My check engine light is on,but my jeep runs fine.Anyone have any ideas??
I have a 2001 Jeep Cherokee. Has a 4.0 liter 6 cyl.engine,2wd.The light has been on now for 4 days .I had an oil change and regular maint done on it 3 days ago with no change.It has 134,000 miles on engine.

Answer 5

It can be something as simple as not having the gas cap on tight enough. I drove a Trans Am for 5 years with check engine light on. If it is running okay, I wouldn't worry to much about it but you probably should take it to a garage and let them run it on a diagnostic machine to see what kinds of codes it pulls up. That usually costs about $75 to have that done. You could also go to the parts store and buy your own little diagnostic tool. Go talk to a sales person at your local Auto Zone parts store or Advance Auto store.

It could be anything almost. More than likely a sensor getting ready to go bad. I would go have it checked out to be on the safe side so you don't have to worry about it anymore.

Answer 6

Kragen's won't do it. My 94 Jeep Grand Cherokee always got the check engine light problem and it was never anything important and it would go away, so I stopped taking it to the shop and blowing money on the diagnostics. But with your miles, it wouldn't hurt to have a real shop check it out in case it's an O2 sensor that could be messing with emissions. Better to find out now than to fail a smog test and have to pay for it again after getting it fixed.

Answer 7

The light is NOT a maintenance reminder. It does NOT come on at a predetermined mileage. It is an indicator that the onboard computer has detected a condition outside of the parameters of its programming. Could be 1000s of things ranging from a loose fuel cap to a bad wire. As somebody suggested, take it to Autozone for a free scan, but don't buy what they suggest. The DTC is only going to tell you where the problem was detected, not what the problem is. Post the DTC on here and we will help further.

Answer 8

The 3 biggest possibilities are -1 Check your gas cap, it may not be fitting right, also if you drove with it off you may need your mechanic to just reset the light, sometimes they stay on after that problem is taken care of. 2 You missed your scheduled maintenance or the mechanic just forgot to reset the sensor, newer cars are made with sensors that measure the mileage vs. when you should take it in for checkup, oil-change, that kind of thing. Or 3 Something is wrong with your car, it doesn't have to be making weird noises for something to be wrong. That is why they have those sensors and lights, to tell you as or before something goes wrong. If your car was making noises or whatever then it would have been already to late to correct without replacing which kind of wastes the whole point of early-warnings like those.

Answer 9

You can reset the light by disconnecting the positive or negative side of the battery and leave it off over night. Reconnect the battery and see if the light comes back on. If so, I agree stop at one of the franchise auto places and have them pull the code. The code should lead you to the problem. If you are not comfortable fixing it seek a pro auto repair person.

Answer 10

You can retreive the computer trouble code by doing this-Turn the key on then off then on 3 times,leaving it on the third time.At this point the check engine light will flash a code.Count the short flashes followed by a short pause and more flashes.then a longer pause and another code will display.You will read a code 11[beginning of test] followed by the actual trouble code then a 55[end of test].Repeat as necessary until you're sure of yourself.Post the code here with your vehicle information and someone will interpret it for you.

Answer 11

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A small piece of black electrical tape will fix that just fine. cover the light with the tape and keep driving. If it ain't broke, don't fix it. It could cost you hundreds of dollars to chase the problem down. How much money do you want to put into a rig with over 200K on it?