SFI SYSTEM, Diagnostic DTC:P0504

DTC Code DTC Name
P0504 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 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 stores the DTC.

Tech Tips

The normal conditions are shown in the table below.

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 GTS, 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) The ignition switch is turned to ON.

(b) The STP signal is off when the ST1- signal is off.


  • Open or short in stop light switch signal circuit

  • Stop light switch

  • STOP fuse

  • IGN fuse

  • ECM

WIRING DIAGRAM

A00555ME01

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 GTS. 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 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 conditions can be checked using the GTS.


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON and turn the GTS on.

    3. Enter the following menus: Powertrain / Engine and ECT / Data List / Stop Light Switch and ST1.

    4. Check the Data List indication when the brake pedal is depressed and released.

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

PROCEDURE


  1. CHECK HARNESS AND CONNECTOR (TERMINAL VOLTAGE)


    1. A005601E04
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Switch)

      Disconnect the 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
      A57-6 (B) - Body ground Ignition switch ON 11 to 14 V
      A57-7 (B) - Body ground Always 11 to 14 V
    4. Reconnect the stop light switch assembly connector.


    NG
    OK
  2. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - BODY GROUND)


    1. Disconnect the stop light switch assembly connector.

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

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      A57-2 (GND) - Body ground Always Below 1 Ω
    3. Reconnect the stop light switch assembly connector.


    NG
    OK
  3. CHECK ECM (STP AND ST1- VOLTAGE)


    1. A0058A5E04
      Text in Illustration
      *a Brake Pedal Depressed
      *b Brake Pedal Released
      *c

      Front view of wire harness connector

      (to ECM)

      Disconnect the ECM 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 Brake Pedal Operation Specified Condition
      A67-10 (ST1-) - Body ground Released 11 to 14 V
      Depressed Below 1.5 V
      A67-9 (STP) - Body ground Released Below 1.5 V
      Depressed 11 to 14 V
    4. Reconnect the ECM connector.


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


    1. Disconnect the stop light switch assembly connector.

    2. Disconnect the ECM connector.

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

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      A57-3 (L) - A67-9 (STP) Always Below 1 Ω
      A57-5 (L) - A67-10 (ST1-) Always Below 1 Ω
      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      A57-3 (L) or A67-9 (STP) - Body ground Always 10 kΩ or higher
      A57-5 (L) or A67-10 (ST1-) - Body ground Always 10 kΩ or higher
    4. Reconnect the stop light switch assembly connector.

    5. Reconnect the ECM connector.


    OK
    NG