SFI SYSTEM (w/o Secondary Air Injection 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.

Signal Brake Pedal Released In Transition Brake Pedal Depressed
STP OFF ON ON
ST1- ON ON OFF

Tech Tips

The normal condition of the signals is shown in the table above.

DTC No. DTC Detection Condition Trouble Area
P0504/51

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


  • (a) Ignition switch ON

  • (b) Brake pedal released

  • (c) STP signal is OFF when ST1- signal is OFF

  • Short in stop light switch signal circuit

  • STOP fuse

  • Stop light switch

  • ECM

WIRING DIAGRAM

A01J67QE01

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.

When using intelligent tester:

PROCEDURE


  1. CHECK STOP LIGHT (OPERATION)


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

      OK
      Stop lights turn ON and OFF when brake pedal is depressed and released, respectively.

    NG

    REPAIR OR REPLACE STOP LIGHT SWITCH CIRCUIT

    OK

  2. READ DATA LIST (STP SIGNAL, ST1- VOLTAGE)


    1. 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 and ECT / Data List / Stop Light Switch.

    4. A01J35KE06

      Check the STP signal when depressing and releasing the brake pedal.

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

    5. Measure the voltage of the ECM connectors.

      Standard voltage
      Tester Connection Brake Pedal Condition Specified Condition
      E8-16 (ST1-) - E11-3 (E1) Depressed Below 1.5 V
      E8-16 (ST1-) - E11-3 (E1) Released 7.5 to 14 V

    OK

    CHECK FOR INTERMITTENT PROBLEMS

    NG

  3. INSPECT STOP LIGHT SWITCH ASSEMBLY

    A01J4UPE07

    1. 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 WIRE HARNESS (STOP LIGHT SWITCH - ECM)

    A01J6USE02

    1. Disconnect the E8 and E9 ECM connectors.

    2. Disconnect the S14 stop light switch connector.

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

      Standard resistance
      Tester Connection Specified Condition
      S14-1 - E9-4 (STP) Below 1 Ω
      S14-4 - E8-16 (ST1-) Below 1 Ω
      S14-1 or E9-4 (STP) - Body ground 10 kΩ or higher
      S14-4 or E8-16 (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 (OPERATION)


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

      OK
      Stop lights turn ON and OFF when brake pedal is depressed and released, respectively.

    NG

    REPAIR OR REPLACE STOP LIGHT SWITCH CIRCUIT

    OK

  2. CHECK ECM (STP, ST1- VOLTAGE)

    A01J35KE07

    1. Turn the ignition switch ON.

    2. Measure the voltage of the ECM connectors.

      Standard voltage
      Tester Connection Brake Pedal Condition Specified Condition
      E9-4 (STP) - E11-3 (E1) Depressed 7.5 to 14 V
      E9-4 (STP) - E11-3 (E1) Released Below 1.5 V
      E8-16 (ST1-) - E11-3 (E1) Depressed Below 1.5 V
      E8-16 (ST1-) - E11-3 (E1) Released 7.5 to 14 V

    OK

    CHECK FOR INTERMITTENT PROBLEMS

    NG

  3. INSPECT STOP LIGHT SWITCH ASSEMBLY

    A01J4UPE07

    1. 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 WIRE HARNESS (STOP LIGHT SWITCH - ECM)

    A01J6USE02

    1. Disconnect the E8 and E9 ECM connectors.

    2. Disconnect the S14 stop light switch connector.

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

      Standard resistance
      Tester Connection Specified Condition
      S14-1 - E9-4 (STP) Below 1 Ω
      S14-4 - E8-16 (ST1-) Below 1 Ω
      S14-1 or E9-4 (STP) - Body ground 10 kΩ or higher
      S14-4 or E8-16 (ST1-) - Body ground 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS AND CONNECTOR

    OK

    REPLACE ECM