ECD SYSTEM (w/o DPF), Diagnostic DTC:P0504

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

DESCRIPTION

In this system, the signals of the duplex type stop light switch (STP and ST1-) are used to judge whether the brake system is abnormal. When signals that indicate depressing and releasing the brake pedal are detected simultaneously, the ECM interprets this as a malfunction of the stop light switch circuit.

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

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

(1 trip detection logic)

(a) Ignition switch ON

(b) Brake pedal released

(c) STP signal OFF when ST1- signal OFF

  • Short in stop light switch signal circuit

  • Stop light switch

  • ECM

WIRING DIAGRAM

A01BC2AE01

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 an intelligent tester. Freeze frame data record 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, if the air-fuel ratio was lean or rich, and other data, from the time the malfunction occurred.

PROCEDURE


  1. CHECK OPERATION OF STOP LIGHT


    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. INSPECT ECM (ST1- SIGNAL)


    1. A01BFT2E13

      Connect an intelligent tester to the DLC3.

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

    3. Select the following menu items: Powertrain / Engine / Data List / Stop Light Switch.

    4. Read the value.

      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
      ST1- (B7-14) - E1 (D3-7) Depressed Below 1.5 V
      ST1- (B7-14) - E1 (D3-7) 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 stop light switch resistance.

      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

    3. Reinstall the stop light switch.


    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY

    OK

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


    1. A01BC7AE11

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

    4. Reconnect the ECM connector.

    5. Reconnect the stop light switch connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    REPLACE ECM