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.

Signals (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

Conditions (a), (b) and (c) continue for 0.5 seconds or more (1 trip detection logic):

(a) Ignition switch ON.

(b) Brake pedal is released.

(c) The STP signal is off when the ST1- signal is off, or the STP signal is on when the ST1- signal is on.

  • Open or short in stop light switch assembly signal circuit

  • Stop light switch assembly

  • ECM

 - DTC stored
Related Data List
DTC No. Data List
P0504 Stop Light Switch

CONFIRMATION DRIVING PATTERN

DTC No. DTC Detection Drive Pattern
P0504 Release and depress brake pedal with ignition switch ON

WIRING DIAGRAM

A01QRC9E03

CAUTION / NOTICE / HINT

Note


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

  • After replacing the ECM, the new ECM needs registration (Click here ) and initialization Click here.

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, 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 / 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

PROCEDURE


  1. CHECK TERMINAL VOLTAGE (POWER SOURCE OF STOP LIGHT SWITCH ASSEMBLY)

    A01QTX9C16
    *a

    Front view of wire harness connector

    (to Stop Light Switch Assembly)

    1. Disconnect the stop light switch assembly connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A77-7 (B) - Body ground Always 11 to 14 V
      Result
      Proceed to
      OK
      NG

    NG

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

    OK

  2. CHECK TERMINAL VOLTAGE (POWER SOURCE OF STOP LIGHT SWITCH ASSEMBLY)

    A01QTX9C17
    *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 Condition Specified Condition
      A77-6 (B) - Body ground Engine switch on (IG) 11 to 14 V
      Result
      Proceed to
      OK
      NG

    NG

    CHECK HARNESS AND CONNECTOR (IG2 RELAY - STOP LIGHT SWITCH ASSEMBLY) Click here

    OK

  3. 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
      A77-2 (GND) - Body ground Always Below 1 Ω
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. CHECK TERMINAL VOLTAGE (STP AND ST1- VOLTAGE)


    1. A01QSZEC02
      *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 Condition Switch Condition
      A61-34 (ST1-) - Body ground Released 7.5 to 14 V
      Depressed Below 1.5 V
      A61-35 (STP) - Body ground Released Below 1.5 V
      Depressed 7.5 to 14 V
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE ECM Click here

    NG

  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
      A77-5 (L) - A61-34 (ST1-) Always Below 1 Ω
      A77-3 (L) - A61-35 (STP) Always Below 1 Ω
      A77-5 (L) or A61-34 (ST1-) - Body ground Always 10 kΩ or higher
      A77-3 (L) or A61-35 (STP) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE STOP LAMP SWITCH ASSEMBLY Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  6. CHECK HARNESS AND CONNECTOR (IG2 RELAY - STOP LIGHT SWITCH ASSEMBLY)


    1. Remove the IG2 relay from the engine room relay block and junction block assembly.

    2. Disconnect the stop light switch assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      IG2 relay terminal 5 - A77-6 (B) Always Below 1 Ω
      IG2 relay terminal 5 or A77-6 (B) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    OK

    GO TO ECM POWER SOURCE CIRCUIT Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR