ECD SYSTEM, Diagnostic DTC:P0504

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

DESCRIPTION

The stop light switch assembly 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 that the brake pedal is being depressed and released, are detected simultaneously, the ECM interprets this as a malfunction in the stop light switch assembly and stores the DTC.

Tech Tips

The normal conditions are as shown in the table below.

Signal (ECM terminal) Brake Pedal Released In Transition Brake Pedal Depressed
STP OFF ON ON
ST1- ON ON OFF

DTC No. Detection Item DTC Detection Condition Trouble Area MIL Memory
P0504 Brake Switch "A"/"B" Correlation

When brake pedal is being depressed, STP signal and ST1- signal are OFF.

(2 trip detection logic)

  • Short in stop light switch assembly signal circuit

  • Stop light switch assembly

  • ECM

 Comes on DTC stored
Related Data List
DTC No. Data List
P0504 Stop Light Switch

WIRING DIAGRAM

A01M1V0E01
*a from IG2 Relay
*b from Battery
*c STOP
*d Stop Light Switch Assembly

CAUTION / NOTICE / HINT

Tech Tips


  • When the ECM must be replaced, before replacing the ECM, perform the "Learning Values Save" function using the GTS. Then after installing the new ECM, perform all of the initialization/registrations for the "Learning Values Write" function by following the instructions shown on the GTS display.

  • 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, and other data from the time the malfunction occurred.

  • Stop light switch conditions can be checked using the GTS


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

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

    5. Check Stop Light Switch when the brake pedal is depressed and released.

      Brake Pedal Operation Specified Condition
      Depressed ON
      Released OFF

Note


  • When replacing the ECM, the ECM needs registration and initialization.

    Click here

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

PROCEDURE


  1. CHECK ECM (STP AND ST1- VOLTAGE)

    A01M2O2C02
    *a Brake Pedal Depressed
    *b Brake Pedal Released
    *c

    Front view of wire harness connector

    (to ECM)

    1. 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 Condition Specified Condition
      A50-10 (ST1-) - Body ground Released 11 to 14 V
      Depressed 0 to 3 V
      A50-48 (STP) - Body ground Released 0 to 3 V
      Depressed 11 to 14 V
      Result
      Proceed to
      OK
      NG

    NG

    CHECK STOP LIGHT SWITCH ASSEMBLY (TERMINAL VOLTAGE) Click here

    OK

  2. CHECK WHETHER DTC OUTPUT RECURS


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON and turn the GTS on.

    3. Clear the DTCs.


      Powertrain > Engine and ECT > Clear DTCs

    4. Turn the ignition switch off and wait for 60 seconds or more [A].

    5. Start the engine and wait for 15 seconds or more [B].

    6. Release and depress the brake pedal [C].

    7. Repeat [A] through [C] for the number of trips detected.

    8. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.


      Powertrain > Engine and ECT > Trouble Codes

    9. Confirm that the DTC is not output again.

      OK
      DTC is not output again.
      Result
      Proceed to
      OK
      NG

    OK

    END

    NG

  3. REPLACE ECM


    1. Replace the ECM.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 8 Click here

  4. CHECK STOP LIGHT SWITCH ASSEMBLY (TERMINAL VOLTAGE)

    A01M035C27
    *a

    Front view of wire harness connector

    (to Stop Light Switch Assembly)

    1. Disconnect the stop light switch assembly 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
      A1-2 - Body ground Always 11 to 14 V
      A1-4 - Body ground Ignition switch ON 11 to 14 V
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR Click here

    OK

  5. 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
      Tester Connection Condition Specified Condition
      A1-3 - A50-10 (ST1-) Always Below 1 Ω
      A1-1 - A50-48 (STP) Always Below 1 Ω
      A1-3 or A50-10 (ST1-) - Body ground Always 10 kΩ or higher
      A1-1 or A50-48 (STP) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    GO TO STEP 7 Click here

    OK

  6. REPLACE STOP LIGHT SWITCH ASSEMBLY


    1. Replace the stop light switch assembly.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 8 Click here

  7. REPAIR OR REPLACE HARNESS OR CONNECTOR


    1. Repair or replace the harness or connector.

      Result
      Proceed to
      NEXT

    NEXT

  8. CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON and turn the GTS on.

    3. Clear the DTCs.


      Powertrain > Engine and ECT > Clear DTCs

    4. Turn the ignition switch off and wait for 60 seconds or more [A].

    5. Start the engine and wait for 15 seconds or more [B].

    6. Release and depress the brake pedal [C].

    7. Repeat [A] through [C] for the number of trips detected.

    8. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.


      Powertrain > Engine and ECT > Trouble Codes

    9. Confirm that the DTC is not output again.

      Result
      Proceed to
      NEXT

    NEXT

    END