Misfire Code?

BLESSING EWOBOR

MEMBER
2007 KIA MAGENTIS
4 CYL
2WD
AUTOMATIC
122,353 MILES

The cylinder 3 on the vehicle misfired, during the diagnosis it was observed that the ignition coil on the Cylinder 3 was bad. It was replaced with a new one. After certain weeks the Cylinder was recorded on the same cylinder diagnosis that the ignition coil is bad.
I decided to swap ignition coil on cylinder 1 into cylinder 3 and installed a new ignition coil into cylinder 1, if probably the ignition coil, I installed initially was substandard.
The vehicle works for a while, then the problem occurred again (Bad ignition coil on same cylinder 3). Within two months 4 ignition coils has been replaced on cylinder 3.
What could be the cause?
Could there be any test to confirmed this?
Could I get wire diagram for the ignition system.
Thank you very much.

Friday, March 28th, 2025 AT 2:48 AM

3 Replies

STEVE W.

MECHANIC
15,233 POSTS

Coil failure can be caused normally by excess current flow. You say you swapped the coils; did you also change out the spark plugs? A worn plug will have a wider gap that takes more current to jump the gap. That can place a higher load on the coil and cause failure. Kia vehicles tend to be picky about coils as well. Many of the aftermarket coils don't seem to hold up. The other failure point is if the driver transistor in the PCM shorts out and instead of firing the plug it just locks the coil on. The easy way to test for that is simple, the coils are fed battery power from the main relay on one terminal. The PCM fires the coil in time by grounding the other terminal. To test you just unplug the coil and put a 12-volt test light across the 2 terminals. When you start the engine, the light should pulse every time it fires the coil. What you want to watch is that the light actually goes out. If you connect the light and turn on the ignition the light should be off, if it's on then the coil ground is either shorted to ground or the PCM is shorted. To test if it's the PCM you can disconnect the battery and then unplug connector C01 from the PCM. Then look at the 4 terminals in yellow. Unplug all 4 coils. Now connect a test light to battery positive and go to the harness connector you removed from the PCM. Just touch each of the coil driver pins, you don't want the light to turn on. If it turns on then the wire is shorted to ground. If the light was staying on when you did the first test with the light in place of the coil, but none of the wires show them shorted then the PCM is the likely issue, it is trying to keep coil three on full time, to repair that you replace the PCM.

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