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 and sets the DTC.

Tech Tips

The normal conditions are as shown in the table below. The signals can be read using the intelligent tester.

Signal 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) and (b) continue for 0.5 seconds or more

(1 trip detection logic):

(a) Ignition switch is ON

(b) STP signal is off when ST1- signal is off

  • Open or short in stop light switch signal circuit

  • Stop light switch assembly

  • ECM

WIRING DIAGRAM

A005GUKE02

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.

  • Stop light switch assembly 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 STP signal when the brake pedal is depressed and released.

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

PROCEDURE


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


    1. A005LKNE01
      Text in Illustration
      *a

      Front view of wire harness connector

      (to stop light switch assembly)

      Disconnect the A76 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
      A76-1 (B) - Body ground Always 11 to 14 V

    NG

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

    OK

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


    1. A005JOLE01
      Text in Illustration
      *a

      Front view of wire harness connector

      (to stop light switch assembly)

      Disconnect the A76 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 Switch Condition Specified Condition
      A76-5 (B) - Body ground Ignition switch ON 11 to 14 V

    NG

    CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - INTEGRATION NO. 1 RELAY) Click here

    OK

  3. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - BODY GROUND)


    1. Disconnect the A76 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
      A76-3 (GND) - Body ground Always Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - BODY GROUND)

    OK

  4. INSPECT ECM (STP AND ST1 - VOLTAGE)


    1. Disconnect the A58 ECM connector.

    2. Turn the ignition switch to ON.

    3. A005HTOE02
      Text in Illustration
      *a Brake Pedal Depressed
      *b Brake Pedal Released
      *c

      Front view of wire harness connector

      (to ECM)

      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

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


    1. Disconnect the A76 stop light switch assembly connector.

    2. Disconnect the A58 ECM connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A76-4 (L) - A58-10 (ST1-) Always Below 1 Ω
      A76-2 (L) - A58-9 (STP) Always Below 1 Ω
      A76-4 (L) or A58-10 (ST1-) - Body ground Always 10 kΩ or higher
      A76-2 (L) or A58-9 (STP) - Body ground Always 10 kΩ or higher

    OK

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    NG

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

  6. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - INTEGRATION NO. 1 RELAY)


    1. Remove the No. 1 Integration Relay from the engine room relay block.

    2. Disconnect the A76 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
      A76-5 (B) - 1D-19 Always Below 1 Ω
      A76-5 (B) or 1D-19 - Body ground Always 10 kΩ or higher

    OK

    GO TO POWER SOURCE CIRCUIT Click here

    NG

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