P59 ECM Reading & Writing (2003-2006 GM truck) can be a total pain. You may find the estimated read time might be 15 or more minutes. When you attempt to write it, it may take 15 minutes…or it may fail all together.
To improve your chances of reading or writing, pull the radio and the radio amp fuse from the under hood fuse block, circled by a red star in the photo above.
If you still have issues you can run a temporary DLC (data link connector). You will need a wire for power, ground, and serial data. We use one in the shop, if you need one and are unable to make it yourself email us at support@pcmofnc.com and we will give you a quote on one.
