Fuse 24 blows on GMC jimmy?

It can be problem with gear shift circuit or problem with transmission solenoids.May be any of the solenoid is shorting.

Or the problem with radio wiring.

Here is the wire harness colour code for the stereo harness.

GMC Jimmy Car Radio Wiring Guide
Car Radio Battery Constant 12v+ Wire: Orange
Car Radio Accessory Switched 12v+ Wire: Yellow
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Gray
Car Stereo Dimmer Wire: Brown
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: 6 1/2″
Car Audio Front Speakers Location: Doors
Left Front Speaker Positive Wire (+): Tan
Left Front Speaker Negative Wire (-): Gray
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Dark Green
Car Audio Rear Speakers Size: 6 1/2″
Car Audio Rear Speakers Location: Rear Doors
Left Rear Speaker Positive Wire (+): Brown
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Dark Blue
Right Rear Speaker Negative Wire (-): Light Blue

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BUT if radio wiring checked ok, then it can be solenoid issue:---

These vehicles were well know for the wiring to be cut at the firewall for the transmission harness. There is a sharp edge right behind the engine above the transmission and if the harness is out of its clips it can eventually cut and short the harness. Look carefully at the shift lock solenoid and harness. It is located in different locations depending on floor or column shift.

If it blows with shift input you may have a solenoid or harness problem inside the transmission pan.

remove the pan and inspect the harness inside the transmission. A bad internal harness that includes the main TCC solenoid. That needs to be checked.If its shorting, then it has to be replaced.------------