In this system, the signals of the duplex type stop light switch (STP and ST1-) are used to judge whether the brake system is abnormal. When signals that indicate depressing and releasing the brake pedal are detected simultaneously, the ECM interprets this as a malfunction of the stop light switch.
 

 

HINT:

Normal conditions are shown in the table below.

Toyota fault code list DTC P0504

Signal	Brake Pedal Released	In Transition	Brake Pedal Depressed
STP	OFF	ON	ON
ST1-	ON	ON	OFF

DTC No.	DTC Detection Condition	Trouble Area
P0504	Conditions (a), (b) and (c) continue for 0.5 seconds or more: (1 trip detection logic) (a) Ignition switch is on (IG) (b) Brake pedal is released (c) STP signal is OFF when ST1- signal is OFF	Short in stop light switch signal circuit Stop light switch ECM

 

NOTICE:

After replacing the ECM, the new ECM needs registration and initialization.

1.CHECK STOP LIGHT SWITCH

1. Check if the stop lights turn ON and OFF when the brake pedal is depressed and released.

    

   OK:

   Stop lights turn ON and OFF normally.

 

NG	REPAIR OR REPLACE STOP LIGHT SWITCH

OK

2.CHECK STP SIGNAL

1. Connect the intelligent tester to the DLC3.

2. Turn the ignition switch on (IG) and turn the tester ON.

3. Enter the following menus: Powertrain / Engine and ECT / Data List / Stop Light Switch.

4. Check the result.

    

   OK:

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

 

OK	CHECK FOR INTERMITTENT PROBLEMS

NG

3.INSPECT STOP LIGHT SWITCH

1. Disconnect the A5 stop light switch connector.

2. Measure the resistance of the stop light switch.

    

   Standard resistance:

   Tester Connection	Switch Condition	Specified Condition
   1 - 2	Pin not pushed	Below 1 ?
   3 - 4	Pin not pushed	10 k? or higher
   1 - 2	Pin pushed	10 k? or higher
   3 - 4	Pin pushed	Below 1 ?

3. Reconnect the stop light switch connector.

 

NG	REPLACE STOP LIGHT SWITCH

OK

4.CHECK WIRE HARNESS (STOP LIGHT SWITCH - ECM)

1. Disconnect the A5 stop light switch connector.

2. Disconnect the A12 ECM connector.

3. Measure the resistance of the wire harness side connectors.

    

   Standard resistance:

   Tester Connection	Specified Condition
   A5-1 - A12-35 (STP)	Below 1 ?
   A5-4 - A12-34 (ST1-)	Below 1 ?
   A5-1 or A12-35 (STP) - Body ground	10 k? or higher
   A5-4 or A12-34 (ST1-) - Body ground	10 k? or higher

4. Reconnect the stop light switch connector.

5. Reconnect the ECM connector.

 

NG	REPAIR OR REPLACE HARNESS AND CONNECTOR

OK
REPLACE ECM