Code 306/Reset

Yesterday while driving to work I noticed my car sputtering when I began to excelerate and then the CEL came on. Well it did it some more yesterday afternoon but after sitting for about 7 hours while I was at work I drove it home last night without any issue. Then this morning drove around running errands and not one sign of sputter at all. Stopped by the Kia dealership and they read the code which I believe was 306 and they said it was showing the number 6 cylinder misfiring/spark plug/wire problem. They said it could be a bad plug or wire or coil but woulnd’t know till they looked at it which they will in about a week. But still driving and no signs of any sputter. What might have caused the temp sputter and code and how do I reset the CEL to see if the code goes off again?

Car: 2002 Kia Sedona
Milage: 147,000
Eng: 6 cylinder

It sounds like the code was P0306, as that is the code for misfire on the #6 cylinder. The possible causes of this problem include…
a faulty spark plug or wire
a faulty coil pack
a faulty oxygen sensor
a faulty fuel injector

More often than not, a fouled/aged spark plug is the problem, but potentially any of the items on the above list could be the culprits. This engine should have had its spark plugs replaced at least once already, at 90k miles, and is coming up on its second spark plug replacement. When–if ever–were the spark plugs replaced?

If you disconnect the battery for a few minutes, that should get the CEL to extinguish itself and reset the memory of the OBD system.

Incidentally, I hope that when the light was lit up, that it was steadily illuminated. A steady CEL means that it is safe to drive–for the time being–until you can have repairs made. But, if the light is blinking/flashing, that means REPAIR IMMEDIATELY, before you wind up doing very expensive damage to the engine and the catalytic converter.

Bought the van in Aug of 10, had about 135,000 miles then and have put 12,000 miles on since. No clue when of if the plugs were ever changed. CEL came on once then went off few minutes later came back on and has not blinked or gone off since, just on.

Disconnect one of your battery cables for a minute or two…That should clear the CEL. It will also erase the stored code from the computer…

“Bought the van in Aug of 10, had about 135,000 miles then and have put 12,000 miles on since. No clue when of if the plugs were ever changed.”

Hmmmm…Don’t ask, don’t tell–car maintenance version?


As we frequently advise on this board, if you make the mistake of buying a used car that did not come with full maintenance records, you have to assume that NONE of the prescribed maintenance has ever been done. In the case of your vehicle, if the previous owner knew that he was going to get rid of it in the next year or so, he may have gambled with ignoring the very major 90k mile service–knowing that the next owner would be more likely to suffer the consequences of lax maintenance than he was.

So–you need to take out the Owner’s Manual (You DO have one, I hope), and turn to the section for the Kia Maintenance Schedule. Make a list of everything that is listed for the 90k mile service, and have that done. The list will likely include changing all fluids, all filters, and the spark plugs. You would be wise to add a transmission fluid change to the list if it is not listed by the mfr. There is a very good chance that just bringing the vehicle up to date with necessary maintenance will resolve the misfire problem.

Also, take a look to see when the timing belt is supposed to be replaced on this engine. Most likely it was supposed to have been replaced at 105k miles or 7 years, whichever came first. In this case, in the absence of maintenance records, you also have to assume that this vital service has never been done, simply because when that timing belt snaps (not IF is snaps) your engine will become a steaming mass of damaged metal in about one milisecond. And–no–it is not possible to look at a timing belt to determine if it needs to be changed. It can look pristine and can snap 5 minutes later, thus causing valves and pistons to collide, and the engine to immediately cease functioning.

Replacing the timing belt, the water pump, the serpentine belt, and all belt tensioners will likely run about $500, but if you don’t do it, you will have to pay that $500 + a towing and repair bill of perhaps ~$2k when the belt snaps. Clearly, it is not wise to skip this service, so unless you have documentation that the timing belt was replaced already, you need to have it done a.s.a.p., as the current one is living on borrowed time.

So far since purchase I have replaced the starter, the crank shaft sensor all belts and such. have not got to tune up yet…

I had the belt and stuff done at the dealership and they didn’t feel the water pump needed to be changed, plus I didn’t have the $900 they wanted to include it in the change and other non dealerships I spoke to really wanted no part of working on my Kia with changing out the belts and such.

Oh and had the trans fluid changed out, up next is a change out of brake fluid…

Went out today and no CEL…why didn’t it come back on and stay on? Also engine running smooth now for 2 straight days with no sputtering at all.