DTC P1578: Brake System Malfunction: 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.

CHECK FOR DTC (VEHICLE STABILITY CONTROL SYSTEM)
1. Check for DTCs. Refer to DTC CHECK / CLEAR .
  OK
  
  Vehicle stability control system DTCs are not output.
NG → See step 3

OK: 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 P1578 is not output.
NG → See step 5

OK → See step 4
GO TO VEHICLE STABILITY CONTROL SYSTEM. Refer to DIAGNOSTIC TROUBLE CODE CHART
USE SIMULATION METHOD TO CHECK. Refer to HOW TO PROCEED WITH TROUBLESHOOTING
REPLACE ECM. Refer to REMOVAL