ECD 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 that 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 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

  • [OFF] denotes ground potential.

  • [ON] denotes battery potential (+B).

  • On the GTS, both the Data List items Stop Light Switch and ST1 are ON when the brake pedal is depressed because the ST1 indication characteristic is opposite to the Stop Light Switch indication.

DTC No. DTC Detection Condition Trouble Area
P0504

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

(2 trip detection logic)

  • Short in stop light switch signal circuit

  • Stop light switch assembly

  • ECM
Related Data List
DTC No. Data List
P0504 Stop Light Switch

WIRING DIAGRAM

A01IPDOE02

INSPECTION PROCEDURE

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)

    A01ISB1E01
    Text in Illustration
    *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
      A76-10 (ST1-) - Body ground Released 11 to 14 V
      Depressed 0 to 3 V
      A76-48 (STP) - Body ground Released 0 to 3 V
      Depressed 11 to 14 V

    OK

    CHECK WHETHER DTC OUTPUT RECURS Click here

    NG

    CHECK STOP LIGHT SWITCH ASSEMBLY (TERMINAL B VOLTAGE) Click here

  2. CHECK STOP LIGHT SWITCH ASSEMBLY (TERMINAL B VOLTAGE)


    1. A01IQTJE02
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

      Disconnect the 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
      A55-7 (B) - Body ground Always 11 to 14 V
      A55-6 (B) - Body ground Ignition switch ON 11 to 14 V

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A55-2 (GND) - Body ground Always Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR Click here

    OK

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


    1. 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
      Tester Connection Condition Specified Condition
      A55-5 (L) - A76-10 (ST1-) Always Below 1 Ω
      A55-3 (L) - A76-48 (STP) Always Below 1 Ω
      A55-5 (L) or A76-10 (ST1-) - Body ground Always 10 kΩ or higher
      A55-3 (L) or A76-48 (STP) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR Click here

    OK

  4. REPLACE STOP LIGHT SWITCH ASSEMBLY


    1. Replace the stop light switch assembly Click here.


    NEXT

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here

  5. 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 Click here.

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

    5. Turn the ignition switch to ON 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: Engine and ECT / Trouble Codes.

    9. Confirm that the DTC is not output again.

      OK
      DTC is not output again.

    NG

    REPLACE ECM Click here

    OK

    END

  6. REPAIR OR REPLACE HARNESS OR CONNECTOR


    1. Repair or replace the harness or connector.


    NEXT

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here

  7. REPLACE ECM


    1. Replace the ECM Click here.


    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 Click here.

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

    5. Turn the ignition switch to ON 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: Engine and ECT / Trouble Codes.

    9. Confirm that the DTC is not output again.


    NEXT

    END