DTC P1631: Communication Error from ECM to VSC: Procedure

WARNING: This page is about a different car, the 2012 Lexus GX 460. However, it is still accessible from the selected car via links, so may be relevant.

REPLACE ECM
1. Replace the ECM. Refer to REMOVAL .
NEXT: Go to next step
CHECK FOR DTC
1. Clear the DTCs. Refer to DTC CHECK / CLEAR .
2. Perform the following to make sure the DTC detection conditions are met.
  HINT:
  
  If the detection conditions are not met, the system cannot detect the malfunction.
  1. Drive the vehicle at a speed of 50 km/h (30 mph) or more.
  2. Turn the cruise control switch on.
3. Check for DTCs. Refer to DTC CHECK / CLEAR .
  OK
  
  DTC P1631 is not output.
NG → See step 3

OK → END (ECM IS DEFECTIVE)
REPLACE MASTER CYLINDER SOLENOID (SKID CONTROL ECU). Refer to DISASSEMBLY