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 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 light switch

  • STOP fuse

  • IGN fuse

  • ECM

WIRING DIAGRAM

A00DSRKE01

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 conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, 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 engine switch on (IG) and turn the tester on.

    3. Enter the following menus: 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

PROCEDURE


  1. CHECK STOP LIGHT SWITCH ASSEMBLY (TERMINAL VOLTAGE)

    A00DTVHE01
    Text in Illustration
    *1

    Front view of wire harness connector

    (to Stop Light Switch)

    1. Disconnect the A1 stop light switch connector.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A1-2 (B) - Body ground Always 11 to 14 V
      A1-3 (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. INSPECT STOP LIGHT SWITCH ASSEMBLY

    A00DQCUE03

    1. 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 released Below 1 Ω
      Switch pin pushed 10 kΩ or higher
      3 - 4 Switch pin released 10 kΩ or higher
      Switch pin pushed Below 1 Ω

    3. Reinstall the stop light switch assembly.


    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

  3. CHECK ECM (STP AND ST1- VOLTAGE)

    A00DPVYE54

    1. Disconnect the A40 ECM connector.

    2. Turn the engine switch on (IG).

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A40-35 (ST1-) - Body ground Brake pedal released 11 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 11 to 14 V

    4. Reconnect the ECM connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    REPLACE ECM Click here