ALLISON 2000 TRANSMISSION

HAVE A 2006 INTERNATIONAL 4300 7.3 WITH AN NO REVERSE LIGHTS CUSTOMER INFORMED US ABOUT IT MAY BE AN EXTERNAL SWITCH ON BELL HOUSING. NO SWITCH ON HOUSING(TRANSMISSION IS AN ALLISON 2000 TRANSMISSION). UPON FURTHER INSPECTION WE FOUND THAT THERE IS AN INTERNAL MLP SWITCH AND A PRESSURE SWITCH THAT ACTUATES WITH THE REVERSE LIGHTS IN VALVE BODY. REPLACED THEM AND NOTHING CHANGED,MIND YOU THE TRUCK RUNS FINE OTHER THAN THE REVERSE LIGHTS NOT TURNING ON IN REVERSE. AT THIS POINT I TOTALLY START OVER IGNORING THE CUSTOMERS NOTES. RETRACED FUSES AND WIRES FOUND A TEAR IN A PART OF HARNESS AND FIXED THAT(NOT RELATED TO ISSUE) AND FOUND REVERSE LIGHTS HAD A FUSE THAT WAS BAD. SO I REPLACED THAT FUSE AND NOW I HAVE NO CRANK/NO START. ONLY GOOD NEWS IS I CAN JUMP THE STARTER AND I HAVE REVERSE LIGHTS NOW THOUGH. BUT NO START/CRANK IN PARK WITH KEY. ANY IDEAS?

 

Well what ended up happening is we had a similar vehicle come in a 2009 Chevy 3500 HD with the same Allison transmission. we swapped out the TCM to see if there was a difference and turns out we had more functionality with that TCM. So putting two and two together we came to the conclusion that the blown fuse was due to the TCM shorting its self out. So all roads lead to the computer.