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 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 Detection Drive Pattern DTC Detection Condition Trouble Area
Depress and release brake pedal with engine switch on (IG)

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

(1 trip detection logic):

(a) Engine switch on (IG).

(b) Brake pedal is released.

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

  • Open or short in stop light switch signal circuit

  • Stop light switch assembly

  • ECM

WIRING DIAGRAM

B001F31E03

CAUTION / NOTICE / HINT

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, 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 engine switch on (IG).

    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

PROCEDURE


  1. INSPECT STOP LIGHT SWITCH ASSEMBLY (B VOLTAGE)

    B001GSRE02
    Text in Illustration
    *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
      A85-1 (B) - Body ground Always 11 to 14 V
      A85-5 (B) - Body ground Engine switch on (IG) 11 to 14 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - NO.1 INTEGRATION RELAY, BATTERY)

    OK

  2. 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
      A85-3 (GND) - Body ground Always Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. INSPECT ECM (STP AND ST1- VOLTAGE)

    B001CXKE02
    Text in Illustration
    *a Depressed
    *b Released
    *c

    Rear view of wire harness connector

    (to 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 Brake pedal condition Specified Condition
      G185-12 (ST1-) - Body ground Released 7.5 to 14 V
      Depressed 0 to 1.5 V
      G185-13 (STP) - Body ground Released 0 to 1.5 V
      Depressed 7.5 to 14 V

    OK

    REPLACE ECM Click here

    NG

  4. CHECK HARNESS OR 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
      A85-2 (L) - G185-13 (STP) Always Below 1 Ω
      A85-4 (L) - G180-12 (ST1-) Always Below 1 Ω
      A85-2 (L) or G185-13 (STP) - Body ground and other terminals Always 10 kΩ or higher
      A85-4 (L) or G185-12 (ST1- ) - Body ground and other terminals Always 10 kΩ or higher

    OK

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR