Thank you all I found the problem
The reverse signal from switch dose not reach to the computer because the wire is disconnected.

i have a cat that sometimes gives a code of f16 and does not go reverse.
Can you help me

josh,
you should have 4 to 6 ohms on coils (which you confirmed)
also check voltages
white and yellow wires should read battery volts B+
green wire should be battery neg B-

To confirm voltages that is

Swoop I have a unit p6000 hiving a similar code 85 not 87 my particular unit only throws the no forward code when unit is running and working hard after 1 hour. Truck cools down and no problems leave customer location and call back after unit is running after a while and code returns. My coils ohm out at 6 I'm assuming my forward and reverse solenoid is getting hot and failing what is your input in this would you replace the sokenoid to save the time troubleshooting as my unit will not act up again to confirm halt ages a sokenoid

Thanks swoop223 ill check this

I assume you mean F87?
this is the reverse transmission solenoid error code
there is a service bulletin out on this code
has to do with incorrect voltages to the solenoid

check the voltages
should be battery volts
-white wire B+
-yellow wire B+
-green wire B-

the coils should ohm out between 4-6ohms

this problem could be a bad solenoid
a bad F&R switch
bad wiring in the F&R circuit , ie: a broken wire or bad connection at a connector.