FWIW, the ABS block is new. Like, the $4K part. Additionally, wouldn’t the nanocom point me that direction if it was in need of work?

 

DTC P1590
Rough road signal implausible Drive cycle A:Signal implausible.

Possible causes by suggested order of priority:
^ Connectors C504, ECM C637 (B).
^ Open circuit - C637/34 (RG) to C504/4 (RG).
^ ABS fault.

Connectors C504, ECM C637 (B).
CONNECTOR
^ Check for connector not correctly latched, backed out pins, damaged pins, corroded pins.

Open Circuit - C637/34 (RG) to C504/4 (RG).
OPEN_CIRCUIT
^ Check resistance > 1M Ohm

ABS Fault.
CHECK THE FOLLOWING:
^ Carry out diagnostic checks on the ABS system.
POSSIBLE FAULTS
^ Faulty ABS ECU or wiring.

 

Update for those who care - Now the amigos are gone until I drive about 30 miles, then all but the HDC light comes on. I have a new ABS wire (the long, expensive one) from AB on it's way. We'll see if that kills them for good.

 

Was googling something else related to the three amigos and ran across my own thread that I forgot to close out. The new wire that runs all the way to the ECU didn't fix it. The thing that resolved the issue was replacing the hub yet again with a different, better brand. Hasn't come back since.

 

What brand hub did you go with?

 

I don't remember the brand at the moment, but all the bad ones have been in Eurospare boxes.

 

Solved - Three amigos finally gone after taking out yet another Eurospare hub from Atlantic British and replacing it with an AllMakes hub from Rovers North.

Lesson to all future searchers: new parts don't necessarily allow you to rule them out when troubleshooting.