Diagnosis System [12/2019 - ]

1. If the skid control ECU detects a malfunction, the ABS warning light, brake system warning light (red indicator), brake system warning light (yellow indicator) and slip indicator light will come on in order to warn the driver. Also, if the vehicle is under the following conditions and the brake hold switch (electric parking brake switch assembly) is turned on, the brake hold operated indicator light blinks.
   1. Vehicle Conditions:
      1. The driver door is closed.
      2. The driver seat belt is fastened.

1. When the skid control ECU detects DTCs stored by related systems, it stores DTCs to indicate the malfunctioning system.
   DTC FOR RELATED SYSTEM MALFUNCTION
   
   

   Malfunctioning System	Output DTC	DTC Storage	System/Control Condition
   Hybrid control system	DTC U0293-00 DTC U0293-87 DTC U1150-00 DTC U1150-87 DTC U1492-57	Current and history DTCs are cleared when the system returns to normal.	VSC system is disabled Brake hold control operation is prohibited
   Airbag system	DTC U0151-87	Current DTCs are cleared when the system returns to normal.	Secondary collision brake control operation is prohibited

   HINT: 

   The above DTCs may be stored in the skid control ECU even if it was never stored as a history DTC or cleared in the system that caused the DTC to be stored.

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

When troubleshooting OBD II (On-Board Diagnostics) vehicles, the vehicle must be connected to the scan tool (complying with SAE J1978). Various data in the vehicle's computer can then be read.

OBD II regulations require that the vehicle's on-board computer store an SAE code and illuminate the Malfunction Indicator Lamp (MIL) on the instrument panel when the computer detects a malfunction.