Hello, I have a 02 f350 dually with a 7.3 6 speed . Recently the engine light came on. The idle is rougher than normal and it feels as if it is not running on all 8 cylinders. I ordered a cps, but I just replaced the one on it about 20,000 miles ago. the truck has 103,000 miles on it. This problem haappened when I went to start it 2 days ago. I noticed the rough idle and the light came on. I shut it off at the gas station and re started and it ran fine with no engine light.after that the light has come on every time. I tried auto zone to check for code's but aparently the guy I purchased the truck from had a chip in it .he asked me if the cruise controll and the 12volt power supply worked. both do not work on my truck, never have. I was then told that the chip damaged the ecm and it would not throw any codes???????????? BS or not? any help would be appreciated. Thanks for your time. Jim the concrete guy.