SFI SYSTEM, Diagnostic DTC:P0504

DTC Code DTC Name
P0504 Brake Switch "A" / "B" Correlation

DESCRIPTION

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 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 stores the DTC.

Tech Tips

The normal conditions are 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
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) The ignition switch is turned to ON.

(b) The brake pedal is released.

(c) The STP signal is off when the ST1- signal is off.

  • Open or short in stop light switch assembly signal circuit

  • Stop light switch assembly

  • ECM

WIRING DIAGRAM

A00DT4LE01
A00DQG2E01

INSPECTION PROCEDURE

Note

Inspect the fuses for circuits related to this system before performing the following inspection procedure.

Tech Tips


  • Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, 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.

  • STP signal conditions can be checked using the intelligent tester.


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

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

    5. 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

PROCEDURE


  1. CHECK STOP LIGHT SWITCH ASSEMBLY (TERMINAL VOLTAGE)


    1. A00DQ8DE01
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

      Disconnect the stop light switch assembly connector.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A1-3 - Body ground Ignition switch ON 11 to 14 V

    3. Reconnect the stop light switch assembly connector.


    NG

    CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - INTEGRATION RELAY [IG2]) Click here

    OK

  2. CHECK STOP LIGHT SWITCH ASSEMBLY (TERMINAL VOLTAGE)


    1. A00DQ8DE01
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

      Disconnect the stop light switch assembly connector.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A1-2 - Body ground Always 11 to 14 V

    3. Reconnect the stop light switch assembly connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - BATTERY)

    OK

  3. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. Inspect the stop light switch assembly Click here.


    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

  4. CHECK ECM (STP AND ST1- VOLTAGE)


    1. A00DPVYE55

      Disconnect the ECM connector.

    2. Turn the ignition switch to ON.

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

      Standard Voltage
      Tester Connection Brake Pedal Operation Specified Condition
      A40-35 (ST1-) - Body ground Brake pedal released 7.5 to 14 V
      Brake pedal depressed Below 1.5 V
      A40-36 (STP) - Body ground Brake pedal released Below 1.5 V
      Brake pedal depressed 7.5 to 14 V

    4. Reconnect the ECM connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - ECM)

    OK

    REPLACE ECM Click here

  5. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - INTEGRATION RELAY [IG2])


    1. A00DUQLE01
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Stop Light Switch Assembly)
      *2 Engine Room No. 1 Relay Block
      *3

      Front view of wire harness connector

      (to Integration Relay)

      Disconnect the stop light switch assembly connector.

    2. Remove the integration relay from the engine room No. 1 relay block.

    3. Disconnect the integration relay connector.

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

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      A1-3 - 1A-4 Always Below 1 Ω
      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      A1-3 or 1A-4 - Body ground Always 10 kΩ or higher

    5. Reconnect the integration relay connector.

    6. Reinstall the integration relay.

    7. Reconnect the stop light switch assembly connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - INTEGRATION RELAY [IG2])

    OK

    CHECK ECM POWER SOURCE CIRCUIT Click here