ECD SYSTEM, Diagnostic DTC:P0504/51

DTC Code DTC Name
P0504/51 Brake Switch "A" / "B" Correlation

DESCRIPTION

In this system, the signals of the stop light switch's duplex system (STP and ST1-) are used to judge whether the brake system is abnormal or not. When the signals of depressing and releasing the brake pedal are detected simultaneously, the ECM interprets this as a malfunction of the stop light switch.

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 Condition Trouble Area
P0504/51

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


    1. Ignition switch is ON

    2. Brake pedal is released

    3. STP signal is OFF when ST1- signal is OFF

  • Short in stop light switch signal circuit

  • Stop light switch

  • ECM

WIRING DIAGRAM

A01BHZQE01

INSPECTION PROCEDURE

Note

After replacing the ECM, the new ECM needs registration Click here and initialization Click here.

Tech Tips

Read freeze frame data using the 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 help determine if the vehicle was running or stopped, if the engine was warmed up or not, and other data from the time the malfunction occurred.

When using intelligent tester:

PROCEDURE


  1. CHECK STOP LIGHT CIRCUIT


    1. Check if the stop light turn ON and OFF when the brake pedal is depressed and released.

      OK
      Stop light turn ON and OFF normally.

    NG

    REPAIR OR REPLACE STOP LIGHT SWITCH CIRCUIT

    OK

  2. READ VALUE USING STP SIGNAL


    1. A01BFT2E01

      Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch ON and turn the intelligent tester ON.

    3. Enter the following menus: Powertrain / Engine / Data List / Stop Light Switch.

    4. Check the result.

      OK
      Brake Pedal Specified Condition
      Depressed STP signal ON
      Released STP signal OFF

    5. Measure the voltage of the ECM connectors.

      Standard voltage
      Tester Connection Brake Pedal Specified Condition
      B7-14 (ST1-) - D3-7 (E1) Depressed Below 1.5 V
      B7-14 (ST1-) - D3-7 (E1) Released 7.5 to 14 V

    OK

    CHECK FOR INTERMITTENT PROBLEMS

    NG

  3. CHECK STOP LIGHT SWITCH ASSEMBLY


    1. A01BBYWE05

      Remove the stop light switch.

    2. Measure the resistance of the switch.

      Standard resistance
      Tester Connection Switch Condition Specified Condition
      1 - 2 Pin not pushed Below 1 Ω
      3 - 4 Pin not pushed 10 kΩ or higher
      1 - 2 Pin pushed 10 kΩ or higher
      3 - 4 Pin pushed Below 1 Ω

    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY

    OK

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


    1. A01BC7AE01

      Disconnect the B2 stop light switch connector.

    2. Disconnect the B7 ECM connector.

    3. Measure the resistance of the wire harness side connectors.

      Standard resistance
      Tester Connection Specified Condition
      B2-1 - B7-15 (STP) Below 1 Ω
      B2-4 - B7-14 (ST1-) Below 1 Ω
      B2-1 or B7-15 (STP) - Body ground 10 kΩ or higher
      B2-4 or B7-14 (ST1-) - Body ground 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS AND CONNECTOR

    OK

    REPLACE ECM

When not using intelligent tester:

PROCEDURE


  1. CHECK STOP LIGHT CIRCUIT


    1. Check if the stop lights turn ON and OFF when the brake pedal is depressed and released.

      OK
      Stop lights turn ON and OFF normally.

    NG

    REPAIR OR REPLACE STOP LIGHT SWITCH CIRCUIT

    OK

  2. CHECK ECM TERMINAL VOLTAGE (STP AND ST1- TERMINALS)


    1. A01BFT2E02

      Turn the ignition switch ON.

    2. Measure the voltage of the ECM connectors.

      Standard voltage
      Tester Connection Brake Pedal Condition Specified Condition
      B7-15 (STP) - D3-7 (E1) Depressed 7.5 to 14 V
      B7-15 (STP) - D3-7 (E1) Released Below 1.5 V
      B7-14 (ST1-) - D3-7 (E1) Depressed Below 1.5 V
      B7-14 (ST1-) - D3-7 (E1) Released 7.5 to 14 V

    OK

    CHECK FOR INTERMITTENT PROBLEMS

    NG

  3. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. A01BBYWE05

      Remove the stop light switch.

    2. Measure the resistance of the switch.

      Standard resistance
      Tester Connection Switch Condition Specified Condition
      1 - 2 Pin not pushed Below 1 Ω
      3 - 4 Pin not pushed 10 kΩ or higher
      1 - 2 Pin pushed 10 kΩ or higher
      3 - 4 Pin pushed Below 1 Ω

    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY

    OK

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


    1. A01BC7AE01

      Disconnect the B2 switch connector.

    2. Disconnect the B7 ECM connector.

    3. Measure the resistance of the wire harness side connectors.

      Standard resistance
      Tester Connection Specified Condition
      B2-1 - B7-15 (STP) Below 1 Ω
      B2-4 - B7-14 (ST1-) Below 1 Ω
      B2-1 or B7-15 (STP) - Body ground 10 kΩ or higher
      B2-4 or B7-14 (ST1-) - Body ground 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS AND CONNECTOR

    OK

    REPLACE ECM