Cat TH 360B no start no movement

I am trying to fix this 360B for my daughters house builder, it came to me on a chain. You can get it to start if you jump the solenoid on the starter, if you use the start position on the switch it applies 1.5 volts to circuit 306 on the start relay which doesn't trip the relay to apply power to the starter. Once started the machine shows it is in neutral and never tries to move no matter the shift lever position. All hydraulics work once started. I believe it might be a 2004 model. Is there any place that a person can go to get wiring diagrams that is legit besides Cat? I can test 12 volts on orange wire at switch when in start position but not sure what interlocks it must travel through before it turns into a green wire labeled 306. I would like to help this guy out, any help or direction to seek help would be much appreciated, thanks.

Shifter always shows neutral no matter which gear or direction is selected.

Unplug the shifter and see if it starts. The safety neutral is built into the shifter. It sounds to me that you have a bad shifter. Also check the connection for moisture. That can mess with it also. Good luck and I hope this helps.

I disconnected shifter and it didn't start.... The white wire has 12 volts and black has ground, light green and brown wires are twisted and have 2.7 volts on each so I would think maybe they are data lines and the shifter is like a module. When the shifter is unplugged the instrument cluster displays that it is still in neutral. The connector is dry and the shifter seems dusty like it might not have been wet, but I'm not sure. There is a good chance water is the start of this machines problems since the window doesn't close right on the door and is held close with a bungee cord. Paul I feel like you are on the right path and I am tempted to disassemble shifter and see what is going on inside...

Talked to the owner and he said he had a cat tech out to look at it and they tried a different shifter with no solution to the movement problem. I had a helper hold the key in the start position and used a thermal imaginer to follow along the loom from ignition to computer and even underhood, the only spots with heat was the main disconnect switch and a 120 ohm shorting plug that is circuit 308 a yellow wire near the starter relay, it gets 12 volts when the key is in the start position. I have tried jumpering the plug; no help. I'm about out of things to do and try without a construction equipment scan tool and/or wiring diagrams.

I can't believe that I didn't mention this first. Check to see if the park brake switch is engaged in the proper position, and if it is working correctly. This would also lock out the starter.

Yes the parking brake is applied and changes the light on cluster as I apply and release it. I did find the Access Platform 10 amp fuse blown with B+ on one side of it and 10 volts on the other leg of it. So to me that seems like 10 volts is backfeeding into that circuit. If I go to the tail of the machine in access hole I can unplug the cord that goes up the boom and the 10 volts goes away, I thought maybe that would bring everything back to life but it didn't. Still no voltage difference on data lines. I unplugged transmission, engine, main computer, shifter, instrument cluster, and access platform cable and still no communication is restored. I contacted CAT and the service manual is $918, which I think the owner would buy it but the I'm hesitant that even with that I might still need a scan tool to help fix this machine. I am about out of ideas and talent, lol. I did try to call the CAT repairman to offer my garage to work on it and he can take back over but no return call yet. I feel like wires are pinched in the boom and are shorting the data line out even though I might have some of it unplugged....

The CAT service guy came back and hooked up his computer and no communication, he was done again with it.... I looked through the wiring diagrams and saw the ignition switch wire fed straight to the main computer, trying to diagnose the simplest circuits first I set my sights on that again. Power at switch, none at computer... half-way point was the bulk head connector at back of cab, none there.... so then I started dissembling the dash and the wire loom goes behind a side panel that makes a nice restraint for mice to sit and eat wiring. About 20 wires maybe less was damaged and I just checked one by one and replaced one by one. The machine fired up on its own and moves as designed. The owner is happy and I got some trading down to have him do some things to my house that I didn't want to. Thanks for your time!

Always glad to hear a success story.