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 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

  • [OFF] denotes ground potential.

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

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

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 is on (IG).

(b) Brake pedal is released.

(c) STP signal is OFF when the ST1- signal is OFF.

  • Short in stop light switch signal circuit

  • STOP fuse

  • IGN fuse

  • Stop light switch assembly

  • ECM

WIRING DIAGRAM

A01EPQ2E08

INSPECTION PROCEDURE

Note

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

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, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

  • STP signal conditions can be checked using the GTS.


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

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

    5. 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. READ VALUE USING GTS (STOP LIGHT SWITCH)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

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

    5. Read the value displayed on the GTS.

      Standard
      Condition Specified Condition
      Brake pedal depressed STP signal ON
      Brake pedal released STP signal OFF

    NG

    INSPECT STOP LIGHT SWITCH ASSEMBLY (B+ VOLTAGE) Click here

    OK

    CHECK FOR INTERMITTENT PROBLEMS Click here

  2. INSPECT STOP LIGHT SWITCH ASSEMBLY (B+ VOLTAGE)

    A01EPLAE23
    Text in Illustration
    *a

    Front view of wire harness connector

    (to Stop Light Switch)

    1. Disconnect the stop light switch connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A30-2 - Body ground Always 11 to 14 V
      A30-4 - Body ground Engine switch on (IG) 11 to 14 V

    NG

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

    OK

  3. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. Inspect the stop light switch assembly Click here.


    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

  4. INSPECT ECM (STP AND ST1 - VOLTAGE)

    A01ERJ7E03
    Text in Illustration
    *a Depressed
    *b Released
    *c

    Front view of wire harness connector

    (ECM)

    1. Disconnect the 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
      A53-35 (ST1-) - Body ground Brake pedal released 7.5 to 14 V
      Brake pedal depressed Below 1.5 V
      A53-36 (STP) - Body ground Brake pedal released Below 1.5 V
      Brake pedal depressed 7.5 to 14 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    REPLACE ECM Click here