Hello: my brother's sebring with the 2.4 VVT engine was overheated. I don't know how severely it was overheated, but when I replaced the upper rad hose assembly (the filler neck part cracked, causing coolant loss) and refilled the coolant and started the car, it was difficult to start: in fact, it seemed to at first be pushing coolant back out of the filler neck, which led me to suspectpossible blown head gasket. However, it did start, but ran rather roughly, with intermittent misfires. I let it warm up, and it didn't seem to be overheating anymore, but the etc light was flashing, and it was definitely down on power. The MIL was on, and there were quite a few obd codes stored, including knock sensor, coolant temp, etc. I was wondering if erasing the codes or disconnecting the battery could reset the system back to normal, or if there was actually engine damage done. Any input/ideas are welcome.Thanks

 

Erasing the codes will only make it more difficult for a qualified repairman to actually find out what's going on in there so he can start to fix it. Codes don't make the engine run badly. Bad things going on generate codes. Somebody is going to need to get in there and arrive at a proper diagnosis and he'll need all the information he can gather.