My service engine soon light came on. I turned off the engine and the light goes out. then about 5 miles later the light came back on. The car runs fine and the gas cap is on tight. What could the problem be?

O2 sensors can cause this and often they clear up after a good run.

In most cases the check engine light indicates a sensor is bad. Have a mechanic scann it and if so replace it.....hope this info helps and if so Please leave rating on this post and good luck..

Are you sure you have EGR flow?? Hold the EGR valve open the engine should run poorly, if not you have no flow.

yes the check engine light has to be on for a while. so they can get the problem codes with an OBD-II scanner to find what area the problem is in.

remove dog house locate test port and install guage should be 45-60 psi

u can rest buy unless the faulty part is replaced you will have the light back on in about 30 miles
TO RESET LIGHT DISCONNECT NEGATIVE BATTERY CABLE FOR 5 MIN'S

IS THIS THE SERVICE ENGINE SOON LIGHT? IF SO IT IS JUST GOING THROUGH SELF TEST, THIS IS NORMAL.

any running problems?

Disconnect the battery, wait 5 minutes, then re-connect it. If that does not work, take it to the dealer. You may not have a problem other than the computer says it is time to turn it on. You may have noticed the same problem about 50-60K miles ago.

I had the same indications on My 2000 Maxima but the engine was also running rough . I replaced the number 3 cylinder ignition module and all of the spark plugs and all of the error lights are back to normal I had to reset the check engine light by disconnecting the battery for about 15 minutes.By the way my car has 253,000 miles on it so if you have a lot of miles on your car you might want to check all of the ignition modules so pull your spark plugs and read them they might tell you where your problem is .