2011 LT - No start, #12 30A fuse blowing

[Spacenerd87]

No check engine light, no codes.
90k miles
V6 Automatic

I've been fighting this issue for a couple months now. My car will not start and blows the #12 30a (starter) fuse each time the ignition is turned to start position, but not the on or acc position.

Checked battery, replaced starter, replaced 30A, checked the wiring harness in the trunk and engine bay, checked grounds in trunk and engine bay. Replaced ignition switch, tested alternator. All other functions of the vehicle work normally.

Not sure where else to look. It appears to be a short to ground somewhere, but everything I've checked looks fine. I have not done any actual voltage testing, just physical checking for loose grounds.

I had this same problem 3 months prior, at first I was able to just pop a new fuse in and it would start, then that stopped working and I had to replace the starter relay. That worked for a day and then the next it didn't. I replaced the starter and it didn't work at first until I got under and reseated the starter connections. After that I was fine for 3 months.

I put a full tank of gas one morning and the #12 fuse blew again which led to me getting it towed home and I've had it on air ever since. For the hell of it I swapped the newish starter for another new one since it was in warranty.

Any ideas? Thank you.

[Mouse330]

I think you have an internal issue with the underhood fuse block. Power is supplied to it from the battery through a cable junction block, fusible link, To the alternator and then to the UFB. Not blowing any other fuses except the 30 amp starter fuse in the start position. Under the UFB is three big connectors X1, X2, and X3. X1 is the largest, X3 is the smallest right next to X1. The starter feed wire is in X3, What I would do in the situation is to try to isolate by disconnecting components, connectors to see what changes. If u access X3 and disconnect it then put the key in the start position, Does it blow?? I've seen a lot of UFB problems in GM and other makes also. Good luck

[Spacenerd87]

Originally Posted by Mouse330

I think you have an internal issue with the underhood fuse block. Power is supplied to it from the battery through a cable junction block, fusible link, To the alternator and then to the UFB. Not blowing any other fuses except the 30 amp starter fuse in the start position. Under the UFB is three big connectors X1, X2, and X3. X1 is the largest, X3 is the smallest right next to X1. The starter feed wire is in X3, What I would do in the situation is to try to isolate by disconnecting components, connectors to see what changes. If u access X3 and disconnect it then put the key in the start position, Does it blow?? I've seen a lot of UFB problems in GM and other makes also. Good luck

Thank you for the reply. So I went ahead with this and disconnected X3 (smallest) next to X1. I put the key to start position and thenfuse did not blow.

[2013ZL1FUN]

Apparently this fixed your issue?

[Mouse330]

Originally Posted by Spacenerd87

Thank you for the reply. So I went ahead with this and disconnected X3 (smallest) next to X1. I put the key to start position and thenfuse did not blow.

Have you resolved the issue?