Hand-held tester:

WARNING: This page is about a different car, the 2004 Lexus ES 330. However, it is still accessible from the selected car via links, so may be relevant.

CHECK OPERATION OF STOP LAMP
1. Check if the stop lamps go on and off normally when the brake pedal is depressed and released.
NG: REPAIR OR REPLACE STOP LAMP SWITCH CIRCUIT

OK: GO TO NEXT STEP.
INSPECT STOP LAMP SWITCH ASSY
1. Check for continuity between each pair of the terminals.
  Standard:
  
  Fig 1: Stop Lamp Switch Terminals Continuity Chart
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  Fig 2: Identifying Stop Lamp Switch Connector Terminals
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
NG: REPLACE STOP LAMP SWITCH ASSY

OK: GO TO NEXT STEP.
READ VALUE OF HAND-HELD TESTER (STP SIGNAL AND ST1 - VOLTAGE)
1. Turn the ignition switch to ON.
2. On the hand-held tester, select the item: DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL / STOP LIGHT SW. Read the values.
  Standard:
  
  Fig 3: Brake Pedal Specified Condition Table
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
3. Measure the voltage between the specified terminals of the E7 and E8 ECM connectors.
  Standard:
  
  Fig 4: Stop Lamp Switch Terminals Specified Condition Chart
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  Fig 5: Depressing And Releasing Brake Pedal
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
OK: CHECK FOR INTERMITTENT PROBLEMS (See CHECK FOR INTERMITTENT PROBLEMS )

NG: GO TO NEXT STEP.
CHECK HARNESS AND CONNECTOR (STOP LAMP SWITCH - ECM)
1. Disconnect the S13 stop lamp switch connector.
2. Disconnect the E7 ECM connector.
3. Check the resistance between the wire harness side connectors.
  Standard (Check for open):
  
  Fig 6: Stop Lamp Switch And ECM Terminals Specified Condition Chart (Check For Open)
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  Standard (Check for short):
  
  Fig 7: Stop Lamp Switch And ECM Terminals Specified Condition Chart (Check For Short)
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
4. Reconnect the stop lamp switch connector.
5. Reconnect the ECM connector.
  
  Fig 8: Identifying Stop Lamp Switch Connector
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  Fig 9: Connecting E7 ECM Connector
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE ECM (See ECM (3MZ-FE) )