I would suggest checking the reading for the rear motor sense current. It should be around zero after it resets at ignition "on" time. If it looks high (more than a few tenths of an amp), that may be the problem. I had that error with a defective control module I bought for this project years ago. It read 24 amps when the commanded current showed zero. No modulator/motor drive assembly was even connected.

 

Closed at OP's request.