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 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.

Tech Tips

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
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) Engine switch on (IG)

  • (b) Brake pedal released

  • (c) STP signal OFF when ST1- signal OFF

  • Short in stop light switch signal circuit

  • STOP fuse

  • Stop light switch

  • ECM

WIRING DIAGRAM

A01635ZE08

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.

PROCEDURE


  1. READ VALUE USING INTELLIGENT TESTER (STP SIGNAL AND ST1- VOLTAGE)


    1. A015YV6E08

      Connect the intelligent tester to the DLC3.

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

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

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

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

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A5-12 (ST1-) - E6-1 (E1) Brake pedal depressed Below 1.5 V
      Brake pedal released 7.5 to 14 V

    NG

    INSPECT STOP LIGHT SWITCH (POWER SOURCE) Click here

    OK

    CHECK FOR INTERMITTENT PROBLEMS Click here

  2. INSPECT STOP LIGHT SWITCH (POWER SOURCE)


    1. A0160U4E25

      Disconnect the stop light switch.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A22-2 - Body ground Always 11 to 14 V
      A22-3 - Body ground Engine switch on (IG) 11 to 14 V

    3. Reconnect the stop light switch connector.


    NG

    INSPECT FUSE (STOP SW AND IGN FUSE) Click here

    OK

  3. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. A0161RLE07

      Remove the stop light switch assembly.

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

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

    3. Reinstall the stop light switch assembly.


    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

  4. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH - ECM)


    1. A016204E02

      Disconnect the stop light switch connector.

    2. Disconnect the ECM connector.

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

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      A22-1 - A5-13 (STP) Always Below 1 Ω
      A22-3 - A5-12 (ST1-) Always
      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      A22-1 or A5-13 (STP) - Body ground Always 10 kΩ or higher
      A22-3 or A5-12 (ST1-) - Body ground Always

    4. Reconnect the stop light switch connector and ECM connector.


    NG

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

    OK

    REPLACE ECM Click here

  5. INSPECT FUSE (STOP SW AND IGN FUSE)


    1. A0160IJE01

      Remove the STOP SW fuse and IGN fuse from the cowl side junction block RH.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      STOP SW fuse Always Below 1 Ω
      IGN fuse Always Below 1 Ω

    3. Reinstall the STOP SW fuse and IGN fuse.


    NG

    REPLACE FUSE (STOP SW AND IGN FUSE)

    OK

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH POWER SOURCE)