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 signal 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. DTC Detection Condition Trouble Area
P0504

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


  • (a) Engine switch on (IG)

  • (b) Brake pedal released

  • (c) STP signal OFF when ST1- signal OFF

  • Short in stop light switch signal circuit

  • ECU-IG fuse

  • Stop light switch

  • ECM

WIRING DIAGRAM

A01GJYBE03

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 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.

  • Stop light switch conditions can be checked using the intelligent tester.


    1. Connect the intelligent tester to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the intelligent tester on.

    4. Enter the following menus: Powertrain / Engine / Data List / Stop Light Switch and ST1.

    5. Check the Data List indication when the brake pedal is depressed and released.

Brake Pedal Operation Stop Light Switch ST1
Depressed ON ON
Released OFF OFF

PROCEDURE


  1. READ VALUE USING INTELLIGENT TESTER (STP SIGNAL AND ST1- VOLTAGE)

    A01GI0BE01

    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 / Data List / All Data / Stop Light Switch.

    4. Check the STP signal when the brake pedal is depressed and released.

      Standard
      Brake Pedal Operation Specified Condition
      Depressed STP signal ON
      Released STP signal OFF

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A14-12 (ST1-) - E3-1 (E1) Brake pedal depressed Below 1.5 V
      Brake pedal released 7.5 to 14 V

    NG

    CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH - ECM) Click here

    OK

    CHECK FOR INTERMITTENT PROBLEMS Click here

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

    A01GJMDE03

    1. Disconnect the A79 stop light switch connector.

    2. Disconnect the A14 ECM connector.

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

      Standard Resistance (Check for open)
      Tester Connection Condition Specified Condition
      A79-2 (L) - A14-13 (STP) Always Below 1 Ω
      A79-4 (L) - A14-12 (ST1-) Always
      Standard Resistance (Check for short)
      Tester Connection Condition Specified Condition
      A79-2(L) or A14-13 (STP) - Body ground Always 10 kΩ or higher
      A79-4 (L) or A14-12 (ST1-) - Body ground Always

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. REPLACE STOP LIGHT SWITCH ASSEMBLY


    1. Replace the stop light switch assembly Click here.


    NEXT

  4. CHECK WHETHER DTC OUTPUT RECURS (DTC P0504)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the intelligent tester on.

    4. Clear the DTCs Click here.

    5. Turn the engine switch off and wait for at least 30 seconds.

    6. Turn the engine switch on (IG).

    7. Turn the intelligent tester on.

    8. Depress and release the brake pedal.

    9. Enter the following menus: Powertrain / Engine / DTC.

    10. Read the pending DTCs.

      Result
      Result Proceed to
      DTC P0504 is output A
      DTC is not output B

    B

    END

    A

    REPLACE ECM Click here