Originally Posted by
2xLS1
Try pulling the radio and radio amp fuse. If it still won't write then it is likely the chime adapter you used. Some seem to be better than others. About 1/2 the ones I encounter won't let you read/write and the other 1/2 will. You will have to either flash it with a bench harness or pull the radio and disconnect the chime adapter from the harness. This applies to 03-07 classic trucks with RAP. If it has an aftermarket alarm or remote start that ties into the purple data wire on the ALDL plug that will have to be disconnected.