E161 code , on a 102 model ,
Main relay is bad. Stuck open. Replace it. It's right underneath the Main VM.

Code E161 - Lower Valve Error
Reason; Power amplifier could not detect presence of lower valve coil.
Possible Cause/
Corrective Action
Lower valve missing.
Open or short circuit in lower valve or wiring; master control relay missing
or stuck open; main contactor open circuit (especially after it has closed);
communication error due to PMT. Allow PMT to reboot before turning truck
ON. Bad power amplifier.

Hey Bud, I know its an old thread, I am having the same issue, was you problem ever solved.
Please let me know.

Main harness replaced. Still E 161 code. Any ideas?

Pull the three bolts and remove tiller arm. Most likely have a broken wire. With code 161 most likely a can wire broke.

I replace the contactor still code out

code e161
lower valve error
power amp could not detect lower valve
lower valve open or short in wiring, master control relay stuck open power amp bad main contactor open. CAN communication error

Cheers, rick