So heres my setup I have a 2000 ws6 LS1 in my CJ7 and originally it had a TH350 behind it and when it went south I decided to upgrade to a built 4l60E from novak. the harness I'm running is a new conversion harness from psi Conversions and it was originally for a T56, I contacted PSI and bought the 13wire section from them for them to add it to the existing harness to run the 4L60E. I installed the new trans and the new section of harness and used a schematic I found on this site and printed it off. the problem I'm having is that as soon as I put the trans in reverse the fuse in the PSI harness for trans power blows. it only does this in reverse and if I have the fuse out and put it in drive and take off the fuse doesnt blow but the trans does not work right either. it only has drive and reverse and no lockup and never shifts up or down automatically. the only codes for the trans is a p0740 and a p1860 for the TCC PWM and the TCC enable solenoid.

I have had the pan down and replaced the harness, pressure switch, and pressure control valve that novak sent me and try to remedy this issue and it didn't do anything. I have also checked the 13 pin harness 4 times for being in the right slots in the ecm connectors. and just in case anyone is wondering I did flash the ecm over to a ls1/4L60E OS and tune.

So my question is what gets activated when the trans is put into reverse and could be blowing the fuse.

 

Nothing gets activated when you put it in Reverse.
However, the pressure control switch does ground one of the signal lines. It appears that putting the shifter into [1] will ground the same line.
I suspect this signal line is somehow/somewhere shorted to the +12V line going to the trans.

 

Thanks