Diagnostic Trouble Code (DTC) P0504 1AZ-FE

Diagnostic Trouble Code (DTC) P0504 Brake Switch "A" / "B" Correlation

1. Description. Diagnostic Trouble Code P0504
2. Wiring diagram. Diagnostic Trouble Code P0504
3. Inspection procedure. Diagnostic Trouble Code P0504

Description. Diagnostic Trouble Code P0504

The stop light switch is a duplex system that transmits two signals: STP and ST1-. These two signals are used by the ECM to monitor whether or not the brake system is working properly. If the signals, which indicate the brake pedal is being depressed and released, are detected simultaneously, the ECM interprets this as a malfunction in the stop light switch and sets the DTC.

HINT:

The normal conditions are as shown in the table below. The signals can be read using the intelligent tester.

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

Toyota fault codes list

DTC No.	DTC Detection condition	Trouble Area
P504	Conditions (a), (b) and (c) continue for 0.5 seconds or more (1 trip detection logic): (a) Ignition switch on (IG) (b) Brake pedal released (c) STP signal OFF when ST1- signal OFF	Short in stop light switch signal circuit Stop light switch STOP fuse IGN fuse ECM

Wiring diagram. Diagnostic Trouble Code P0504

Inspection procedure. Diagnostic Trouble Code P0504

HINT:

1. Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
2. STP signal conditions can be checked using the intelligent tester.
   1. Connect the intelligent tester to the DLC3.
   2. Turn the ignition switch on (IG) and turn the tester ON.
   3. Select the following menu items: Powertrain / Engine and ECT / Data List / Stop Light Switch.
   4. 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

1.CHECK STOP LIGHT SWITCH ASSEMBLY (TERMINAL VOLTAGE)

1. Disconnect the A5 stop light switch connector.

2. Turn the ignition switch on (IG).

3. Measure the voltage between the terminals of the A5 stop light switch connector and body ground.

   Standard voltage:

   Tester Connections	Specified Conditions
   2 (A5-2) - Body ground	9 to 14 V
   3 (A5-3) - Body ground	9 to 14 V

4. Reconnect the stop light switch connector.

NG	Go to step 4

OK

2.INSPECT STOP LIGHT SWITCH ASSEMBLY

1. Remove the stop light switch assembly.

2. Measure the resistance.

   Standard resistance:

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

3. Reinstall the stop light switch assembly.

NG	REPLACE STOP LIGHT SWITCH ASSEMBLY

OK

3.CHECK ECM (STP AND ST1 - VOLTAGE)

1. Disconnect the A12 ECM connector.

2. Turn the ignition switch on (IG).

3. Measure the voltage between the terminals ST1- and STP of the A12 ECM connector and body ground.

   Standard voltage:

   Tester Connection	Brake Pedal Operation	Specified Condition
   ST1- (A12-35) - Body ground	Released	9 to 14 V
   	Depressed	0 to 3 V
   STP (A12-36) - Body ground	Released	0 to 3 V
   	Depressed	9 to 14 V

4. Reconnect the ECM connector.

NG	REPAIR OR REPLACE HARNESS OR CONNECTOR

OK
REPLACE ECM

4.INSPECT FUSE (STOP AND IGN FUSE)

1. Remove the STOP and IGN fuses from the main body ECU (instrument panel junction block).

2. Measure the resistance.

   Standard resistance:

   Below 1 ?

3. Reinstall the STOP and IGN fuses.

NG	CHECK FOR SHORTS IN ALL HARNESSES AND COMPONENTS CONNECTED TO FUSE

OK
REPAIR OR REPLACE HARNESS OR CONNECTOR