SFI SYSTEM (w/o Secondary Air Injection System), Diagnostic DTC:P0504/51

DTC Code DTC Name
P0504/51 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 sets 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).

DTC No. DTC Detection Conditions Trouble Areas
P0504

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

    (1 trip detection logic):


    1. Ignition switch ON

    2. Brake pedal released

    3. STP signal OFF when ST1- signal OFF

  • Short in stop light switch signal circuit

  • STOP fuse

  • Stop light switch

  • ECM

WIRING DIAGRAM

A01BG7JE01

INSPECTION PROCEDURE

Tech Tips

Read freeze frame data using an intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air-fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.

PROCEDURE


  1. CHECK OPERATION OF STOP LIGHT


    1. Check whether the stop lights turn on and off normally when the brake pedal is depressed and released.

      OK
      Stop lights turn ON when brake pedal is depressed.

    NG

    REPAIR OR REPLACE STOP LIGHT SWITCH CIRCUIT

    OK

  2. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. A01BBYWE06

      Remove the stop light switch assembly.

    2. Measure the resistance.

      Resistance
      Switch Positions Tester Connections Specified Conditions
      Switch pin free 1 - 2 Below 1 Ω
      Switch pin free 3 - 4 10 kΩ or higher
      Switch pin pushed in 1 - 2 10 kΩ or higher
      Switch pin pushed in 3 - 4 Below 1 Ω

    3. Reinstall the stop light switch assembly.


    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY

    OK

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


    1. A01BGD0E01

      Connect an intelligent tester to the DLC3.

    2. Turn the ignition switch to the ON position and turn the tester ON.

    3. Select the following menu items: Powertrain / Engine and ECT / Data List / Stop Light SW.

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

      Standard
      Brake Pedal Operations Specified Conditions
      Depressed STP signal ON
      Released STP signal OFF

    5. Measure the voltage between the terminals of the ECM connectors.

      Voltage
      Tester Connections Brake Pedal Operations Specified Conditions

      ST1- (B9-16)

      - E1 (D1-3)

      		 Depressed Below 1.5 V

      ST1- (B9-16)

      - E1 (D1-3)

      		 Released 7.5 to 14 V

    NG

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

    OK

    CHECK FOR INTERMITTENT PROBLEMS

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


    1. A01BBSHE01

      Disconnect the B2 stop light switch connector.

    2. Disconnect the B7 and B9 ECM connectors.

    3. Measure the resistance.

      Resistance (Check for open)
      Tester Connections Specified Conditions
      Stop light switch (B2-1) - STP (B7-4) Below 1 Ω
      Stop light switch (B2-4) - ST1- (B9-16) Below 1 Ω

    4. Reconnect the stop light switch connector.

    5. Reconnect the ECM connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    REPLACE ECM