If you suspect that the transmission shift controller in an M113-series vehicle is bad, the procedures outlined in IETM TM 9-2350-277-13&P (Oct 14) will help you troubleshoot the component.
But keep in mind that there are two versions of the shift controller. The troubleshooting procedures listed in the TM only work if you’re testing NSN 3010-01-245-2442.
To troubleshoot NSN 3010-01-331-2675, swap out the suspected bad shift controller with a known good shift controller. If the problem persists, at least you’ll know the issue isn’t with the shift controller.
FYI, troubleshooting procedures are being developed that will apply to both versions of the shift controller. The procedures will appear in the next TM update.