Rep Power: 0

Hey guys. My girlfriend has a 2010 Civic Ex all stock and her Check Engine light will come on. Then a few days later it will be off then it will come on again. So i plugged in the code reader and didn't get any trouble codes. So i cleared it and it came right back on. Pluged it in again, still no codes. What is causing it to turn on and off like this?

 
Rep Power: 518

First: Try a different code reader. Not all readers work correctly on all cars.

 
Rep Power: 0

That was my first thought too. She took it to the dealership and their reader did the same thing. Said their wasn't a code, cleared it and it came on again the next day

 
Rep Power: 518

Um, wow.
Was it on at the moment they checked it?


How long will it stay on-- like a few seconds at a time, or maybe a half day?

If you have a code reader of your own available, can you induce your own fault code (unplug an important sensor) just to see if the computer and code reader both recognize there really is a fault?



I have no idea what's going on there, this situation doesn't sound familiar to me.

 
Rep Power: 0

As far as i know it doesnt stay on or off for a certain ammount of time. Its kind of random. The code reader works on my Ej8 Civic. Idk why it wouldnt on her car. I havent tried unplugging something to see if if reads her codes

 
Rep Power: 518

The newer car uses a http://en.wikipedia.org/wiki/CAN_bus (<--Wiki link) Your code reader must be CAN compatible.

It's been in use since.....maybe 2004, 2005ish. Somewhere in that era...was when Hondas PGM tester no longer worked on newer cars and the HDS scanner was released to us. I forget a lot of crap LOL.


Causing a known code, and making sure that code is recognized and can be read correctly by your reader (and then erased too) would at least verify if some things do or don't work correctly.

Something easy like unplug the MAF sensor and start the car up, let it run 15 seconds, shut it off...... then do it a couple more times, should cause a CEL and a known code.

Or unplug the coolant temp sensor if that's easy to reach. Same deal, run it a couple times to set the code.



Then maybe leave a known code in the system (history), drive it until the light comes on again and see if the code got mysteriously erased? (Codes will be erased on their own after so many runs though.)