DTC P0504: Brake Switch "A" / "B" Correlation; DTC P0724: Brake Switch "B" Circuit High: Procedure

WARNING: This page is about a different car, the 2009 Lexus IS 250. However, it is still accessible from the selected car via links, so may be relevant.

CHECK STOP LIGHT (STOP LIGHT OPERATION)
1. Check whether the stop lights turn on and off normally when the brake pedal is depressed and released.
  OK
  
  Stop lights turn ON when brake pedal is depressed.
NG → REPAIR OR REPLACE STOP LIGHT SWITCH CIRCUIT

OK: Go to next step

READ VALUE USING TECHSTREAM (STP SIGNAL AND ST1 - VOLTAGE)

Connect Techstream to the DLC3.

Fig 1: Checking STP Signal When Brake Pedal Is Depressed & Released
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Turn the engine switch on (IG) and turn the tester on.
Enter the following menus: Powertrain / Engine and ECT / Data List / Stop Light Switch.

Check the STP signal when the brake pedal is depressed and released.

Brake Pedal Operation	Specified Condition
Depressed	STP signal ON
Released	STP signal OFF

Measure the voltage according to the value(s) in the table below.

Standard voltage

Tester Connection	Brake Pedal Operation	Specified Condition
ST1- (A5-8) - E1 (E4-7)	Depressed	Below 1.5 V
ST1- (A5-8) - E1 (E4-7)	Released	7.5 to 14 V

OK → CHECK FOR INTERMITTENT PROBLEMS

NG: Go to next step

INSPECT STOP LIGHT SWITCH ASSEMBLY

Remove the stop light switch assembly.

Fig 2: Inspecting Stop Light Switch Assembly
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Measure the resistance according to the value(s) in the table below.

Standard resistance

Switch Position	Tester Connection	Specified Condition
Switch pin free	1 - 2	Below 1 Ω
Switch pin free	3 - 4	10 kΩ or higher
Switch pin pushed in	1 - 2	10 kΩ or higher
Switch pin pushed in	3 - 4	Below 1 Ω

Reinstall the stop light switch assembly.

NG → REPLACE STOP LIGHT SWITCH ASSEMBLY

OK: Go to next step

CHECK ECM (STP, ST1 - VOLTAGE)

Disconnect the A5 and A6 ECM connectors.

Fig 3: Measuring Voltage When Brake Pedal Is Depressed & Released
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Measure the voltage according to the value(s) in the table below.

Standard voltage

Tester Connection	Brake Pedal Operation	Specified Condition
STP (A6-4) - Body ground	Depressed	9 to 14 V
STP (A6-4) - Body ground	Released	0 to 3 V
ST1- (A5-8) - Body ground	Depressed	0 to 3 V
ST1- (A5-8) - Body ground	Released	9 to 14 V

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR

OK → REPLACE ECM