Unable to download boot loader issue resolved

[JHPerformance]

I wanted to share my experience with an 2004 Silverado 5.3 4x4 auto.
I was contacted to tune the truck. I plugged in and started to scan, it would communicate with the PCM and validate the license but it immediately timed out on the boot loader. I restarted the laptop, checked fuses, went through everything. By then the customers battery was getting weak, when the battery weakened it would start to read as usual but kick back and fourth from high to low speed. We charged the battery and the boot loader fail message came back. I found that the customer had an aftermarket radio installed, Pioneer brand. When the battery weakened the radio wasn't interfering with the PCM and read. But with it charged, it was. Pulling the radio fuse didn't fix it because the power was tied into the OBDII port. However, we unplugged the aftermarket radio and it worked just fine. Something in the aftermarket radio was messing with the interface. I've always heard of the aftermarket radio warnings on the GM bulletins but ignored them. I always turn the radio off on every vehicle I tune, but even with it off it was still corrupting my initial read.

I hope my findings are useful to someone in the future. This was a new one on me.

Thanks guys!

[dfrautoworks]

Thanks for the post it helped me today! same year truck with the same radio.....just slid it out and disconnected the plug and bingo!

[matty b]

This applies to ANY components that are tied into the serial data line. Some stuff plugs into the OBD2 port which you obviously need to remove to flash, but others allow for hard wiring and that will screw you up.

[hellbents10]

04 trucks always seem to have more issues, I pull radio/radio amp/seo 1 fuses to read/write.

[2xLS1]

This applies to ANY components that are tied into the serial data line. Some stuff plugs into the OBD2 port which you obviously need to remove to flash, but others allow for hard wiring and that will screw you up.

Aftermarket remote starts are ones that usually tie into the purple data wire on the ALDL plug and are many times hidden behind electrical tape by the installer.

[xx_ed_xx]

Wow my own personal truck I have been dealing with this for a while. Sux is there is a lot settings I have to redo when I plug radio back in. curious if i could put in a bypass switch to disconnect it but keep it powered so i dont lose settings

[Chkengine]

Wow my own personal truck I have been dealing with this for a while. Sux is there is a lot settings I have to redo when I plug radio back in. curious if i could put in a bypass switch to disconnect it but keep it powered so i dont lose settings

You have a splice behind dashboard fuse box, where all communication lines coming together. You have to find it, and put a two way tumbler switch which disconnect at once lines from DLC and PCM and connect them both together with all other modules left in a dark