I will attempt to make this as short and sweet as possible and thank you in advance for taking the time to look at my post. I purchased a used ’03 CTS Luxury Sport Edition 2 and a half years ago with 75k miles. At 115k miles it began to idle when at a standstill and at start up. Prior to this I had an antifreeze leak repaired. After the idle a mechanic had found that 3 of my spark plugs had been flooded with oil. We replaced the manifold gasket seals I believe and all 6 spark plugs. We also replaced three of the coils as they had been soaked in oil for some time. A couple of weeks later he checked to see if oil had flooded the spark plugs again, luckily it did not. He cleaned the throttle body and still the same issue.
Very recently while driving the car suddenly down shifted very hard and the Reduced Engine Power warning came on. I pulled over and reset the codes and it drove me home fine however there was a very noticeable down shift when at 20mph and again at approximately 15mph. I checked all fuses and only found a lighter fuse was blown. I checked all 3 fuse boxes. When I attempted to drive it the next day around the block, the car died on me completely and battery and oil light came on with a beep. I pulled it over and started it 5 minutes later and drove it home where she sits now. The engine codes I am receiving are ECM P0700C and P0318C . The P0318C doesn’t concern me as I believe I know what that issue is, it is the P0700C that I believe pertains to my issue now. I have heard that it could be a bad ECM or a faulty connection with the ECM. I attempted to take it apart and clean it however was unsuccessful in pulling it apart and did not want to damage it.
I intend on taking it to get it completely diagnosed at the dealership as I was informed they are the only way to figure out what each and every issue is. I need to decide if I am going to repair it and keep it or trade it in and any help or advice on the above mention issue will be greatly appreciated. I will not have the money to take it in for at least another month. I am a broke college student so money is certainly an issue for me. Once again thank you in advance for looking at my post.