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 both signals, which indicate the brake pedal is being depressed or 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) Ignition switch is ON

(b) Brake pedal is released

(c) STP signal is off when ST1- signal is off

  • Open or short in stop light switch signal circuit

  • Stop light switch

  • STOP fuse

  • ECM

WIRING DIAGRAM

A005LHZE04

CAUTION / NOTICE / HINT

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 conditions 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 and ST1.

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

      Brake Pedal Operation Stop Light Switch ST1
      Depressed ON ON
      Released OFF OFF

PROCEDURE


  1. READ VALUE USING INTELLIGENT TESTER (STOP LIGHT SWITCH)


    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 / All Data / Stop Light Switch.

    5. Read the value displayed on the tester.

      Standard
      Condition Specified Condition
      Brake pedal depressed STP signal ON
      Brake pedal released STP signal OFF

    OK

    CHECK FOR INTERMITTENT PROBLEMS Click here

    NG

  2. CHECK STOP LIGHT SWITCH (TERMINAL VOLTAGE)


    1. A005LG8E02
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Switch)

      Disconnect the stop light switch connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A38-2 - Body ground Always 11 to 14 V

    3. Reconnect the stop light switch connector.


    NG

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

    OK

  3. CHECK STOP LIGHT SWITCH (TERMINAL VOLTAGE)


    1. A005LG8E02
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Switch)

      Disconnect the stop light switch 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 Switch Condition Specified Condition
      A38-4 - Body ground Ignition switch ON 11 to 14 V

    4. Reconnect the stop light switch connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH - IG2 FUSE)

    OK

  4. INSPECT STOP LIGHT SWITCH


    1. A005GPQE33
      Text in Illustration
      *a

      Component without harness connected

      (Stop Light Switch Assembly)
      *b Not pushed
      *c Pushed

      Remove the stop light switch.

    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 not pushed Below 1 Ω
      Switch pin pushed 10 kΩ or higher
      3 - 4 Switch pin not pushed 10 kΩ or higher
      Switch pin pushed Below 1 Ω

    3. Reinstall the stop light switch.


    NG

    REPLACE STOP LIGHT SWITCH Click here

    OK

  5. INSPECT ECM (STP AND ST1 - VOLTAGE)


    1. A005HTOE02
      Text in Illustration
      *a Brake Pedal Depressed
      *b Brake Pedal Released
      *c

      Front view of wire harness connector

      (to ECM)

      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
      A58-10 (ST1-) - Body ground Released 7.5 to 14 V
      Depressed Below 1.5 V
      A58-9 (STP) - Body ground Released Below 1.5 V
      Depressed 7.5 to 14 V

    4. Reconnect the ECM connector.


    OK

    REPLACE ECM Click here

    NG

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