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 stores the DTC.

Tech Tips

The normal switch conditions are as shown in the table below.

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) are met for 0.5 seconds or more (1 trip detection logic):

(a) The engine switch is on (IG).

(b) The brake pedal is released.

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

  • Short in stop light switch signal circuit

  • STOP fuse

  • IGN fuse

  • Stop light switch

  • ECM

WIRING DIAGRAM


B001EAZE02

B001EAZE01

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 GTS. 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 GTS.


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS 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 B VOLTAGE)

    B001I2QE01
    Text in Illustration
    *a

    Front view of wire harness connector

    (to Stop Light Switch)

    1. 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
      A85-1 (B) - Body ground Always 11 to 14 V
      A85-5 (B) - Body ground Engine switch on (IG) 11 to 14 V

    3. Reconnect the stop light switch connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  2. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - BODY GROUND)


    1. Disconnect the stop light switch assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A85-3 (GND) - Body ground Always Below 1 Ω

    3. Reconnect the stop light switch assembly connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. CHECK ECM (STP AND ST1 - VOLTAGE)

    B001H02E01
    Text in Illustration
    *A for Automatic Transmission
    *B for Manual Transmission
    *a Brake Pedal Depressed
    *b Brake Pedal Released
    *c

    Component with harness connected

    (ECM)

    1. Turn the engine switch on (IG).

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

      Standard Voltage
      for Automatic Transmission
      Tester Connection Condition Specified Condition
      G56-34 (ST1-) - Body ground Brake pedal released 11 to 14 V
      Brake pedal depressed 0 to 3 V
      G56-35 (STP) - Body ground Brake pedal released 0 to 3 V
      Brake pedal depressed 11 to 14 V
      for Manual Transmission
      Tester Connection Condition Specified Condition
      G55-8 (ST1-) - Body ground Brake pedal released 11 to 14 V
      Brake pedal depressed 0 to 3 V
      G56-18 (STP) - Body ground Brake pedal released 0 to 3 V
      Brake pedal depressed 11 to 14 V

    OK

    REPLACE ECM Click here

    NG

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


    1. Disconnect the stop light switch assembly connector.

    2. Disconnect the ECM connector.

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

      Standard Resistance (Check for Open)
      for Automatic Transmission
      Tester Connection Condition Specified Condition
      A85-2 (L) - G56-35 (STP) Always Below 1 Ω
      A85-4 (L) - G56-34 (ST1-) Always Below 1 Ω
      for Manual Transmission
      Tester Connection Condition Specified Condition
      A85-2 (L) - G56-18 (STP) Always Below 1 Ω
      A85-4 (L) - G55-8 (ST1-) Always Below 1 Ω
      Standard Resistance (Check for Short)
      for Automatic Transmission
      Tester Connection Condition Specified Condition
      A85-2 (L) or G56-35 (STP) - Body ground Always 10 kΩ or higher
      A85-4 (L) or G56-34 (ST1-) - Body ground Always 10 kΩ or higher
      for Manual Transmission
      Tester Connection Condition Specified Condition
      A85-2 (L) or G56-18 (STP) - Body ground Always 10 kΩ or higher
      A85-4 (L) or G55-8 (ST1-) - Body ground Always 10 kΩ or higher

    4. Reconnect the stop light switch assembly connector.

    5. Reconnect the ECM connector.


    OK

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR