My brother-in-law, who lives 1800 miles away in the boonies, does not have a PC so this question is to assist him. He has a 1999 Mustang GT, 4.6 liter, that runs rough. I instructed him to purchase an OBD2 to diagnose the problem(s). The following 3 DTC codes appeared 1.) P0102 Mass or Volume Air Flow Circuit low Input 2.) P0113 Intake Air Temperature Circuit High Input 3.) P0352 Ignition Coil B Primary/Secondary Circuit Malfunction. While speaking with him on the phone, he stated that he had used brake cleaner on the MAF sensor which is why that code has appeared indicating that he has most likely ruined that sensor, so it needs to be replaced. I suspect that the Intake Air Temp sensor also needs replacement. However, he replaced all 8 ignition coils about a year ago, so it is interesting that the number 2 cylinder coil has the code P0352. He has swapped the number 2 coil with the number 3 coil to see if the error code would change from the number 2 to the number 3 cylinder indicating a code P0353 identifying that the coil has a problem. Question: Since the 3 codes were erased as a result of him disconnecting the battery to swap the coils, and the engine still runs rough since no parts have been replaced, how long does the engine have to run before the DTC codes reappear? Does he have to drive the car to get the codes to reappear?