Usually it is the mass air flow sensor or the O2 sensor. Also, the theft system is known to turn the engine light on.
Why guess when you can go to Auto Zone or other parts stores and have the codes read for free.
Mine Came on after about 100,000 miles and it was just dirty spark plugs. Changes the plugs and the wires and it never came on again. Car was stuttering when going up hills and it fixed that too.
A loose, cracked, or defective gas cap may also be the culprit.
Mine was a small 4.5 inch vacuum hose that was cracked, located right in front on the top of the 2.4L engine. It is an easy & cheap thing to check before replacing sensors.
Transmission Fluid level is low
- I had a temperature sensor malfunctioning and sending a poor mixture of fuel to the engine. When I was accelerating a lot the engine would hesitate and jump. Repair was $200 and works fine now.
I had the same problem with my 2002 Malibu and had to have the catalytic converter replaced in it. You would have to visit the dealer to make sure, because advance or other similar stores cannot tell you what is wrong with it. A sure sign that it needs replaced is if the check engine light stays on and your losing power.
I had a 0403 error on my 98 Malibu and one place said it was the cat converter and both O2 sensors and wanted $550 took it to another place and they said it was just the cat converter and replaced it in 25 min for $220. That fixed the problem and I passed inspection ok.
Just to correct the one above me, I'm assuming that was a P0430, as p0403 would be an EGR code. And most places will not warranty a cat if you don't replace the O2 sensors with it. And not all cat failures involve low power, that only happens if they clog. To answer the original question, there are hundreds of reasons why the CEL can come on. And the theft system will not set a check engine light, though it can store a P1626 in the PCM for excessive cranking. That code doesn't request the check engine light though.
Check your fluid levels.
There are pages and pages of things that can cause a check engine light. You need to have it checked with a scantool. Then the code can be diagnosed and repaired.
I am not sure of the other 4 reasons But in my experience the top reason your check engine light comes on is because your gas cap isn't tightened all the way.
check power to fans,if power check fan sensor!!
Fix the problem causing them to be on.
There is an engine misfire, probably spark plugs issue.
There should be a dipstick like the one for oil. Check with engine running.
Get the computer scanned to see what the problem is.
Disconnect the negative battery terminal for at least 30 seconds.
(torque converter clutch circuit performance or stuck on)
Check your coil pack or the spark plugs.
The light could come on for a number of reasons. The vehivle would have to be hooked up to a scanner to determine the engine code or codes. After you determine the codes you can isolate and fix the probelem. If the check engine light is on there will be a computer code that will appear on the scanner.