SFI 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 both signals, which indicate the brake pedal is being depressed or 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 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 intelligent tester, 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

Conditions (a), (b) and (c) continue for 0.5 seconds or more

(1 trip detection logic):

(a) Ignition switch ON

(b) Brake pedal released

(c) STP signal OFF when ST1- signal OFF

  • Open or short in stop light switch signal circuit

  • Stop light switch assembly

  • ECM

WIRING DIAGRAM

A01VDR5E08
A01VGM5E05

CAUTION / NOTICE / HINT

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 conditions 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 intelligent tester.


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

    4. Enter the following menus: Powertrain / Engine and ECT / 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 (STOP LIGHT SWITCH)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

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

    5. Read the value displayed on the tester.

      OK
      Condition Specified Condition
      Brake pedal depressed STP signal ON
      Brake pedal released STP signal OFF
      Result
      Result Proceed to
      OK A
      NG (for Bulb Type Stop Light) B
      NG (for LED Type Stop Light) C

    A

    CHECK FOR INTERMITTENT PROBLEMS Click here

    C

    CHECK TERMINAL VOLTAGE (POWER SOURCE STOP LIGHT SWITCH ASSEMBLY) Click here

    B

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


    1. A01VI9XE02
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

      Disconnect the stop light switch assembly connector.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A89-2 - Body ground Always 11 to 14 V
      A89-4 - Body ground Ignition switch ON 11 to 14 V
      Result
      Result Proceed to
      NG A
      OK B

    A

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

    B

    INSPECT STOP LIGHT SWITCH ASSEMBLY Click here

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


    1. Disconnect the stop light switch assembly connector.

    2. A01VINKE01
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A101-1 (B) - Body ground Always 11 to 14 V
      A101-5 (B) - Body ground Ignition switch ON 11 to 14 V

    NG

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

    OK

  4. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. Inspect the stop light switch assembly (for Bulb Type Stop Light) Click here.

    2. Inspect the stop light switch assembly (for LED Type Stop Light) Click here.


    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

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


    1. A01VG3TE01
      Text in Illustration
      *a Brake pedal operation
      *b Brake Pedal Depressed
      *c Brake Pedal Released
      *d

      Front view of 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 Operation Specified Condition
      A58-10 (ST1-) - Body ground Released 7.5 to 14 V
      Depressed Below 1.5 V
      A58-9 (STP) - Body ground Released Below 1.5 V
      Depressed 7.5 to 14 V

    OK

    REPLACE ECM Click here

    NG

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