I have a 2005 300c that has developed a surge when it is at a constant speed. I had a code “P3497” pop up, I changed the oil and it went out. About a month ago I had the transmission flushed at the local dealer so the fluids are fresh. I do pull a trailer with this car but the load is under a 1,000 pounds. I am perplexed with this issue, if anyone has any ideas please let me know. Thank you.