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.

Tip:

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

A298904E08

CAUTION / NOTICE / HINT

Note:

Inspect the fuses for circuits related to this system before performing the following inspection procedure.

Tip:

  • 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. U124049E02

      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

      A55-6 (B) - Body ground

      Ignition switch ON

      11 to 14 V

      A55-7 (B) - Body ground

      Always

      11 to 14 V
      Table 1. Text in Illustration

      *a

      Front view of wire harness connector

      (to Stop Light Switch)

    4. Reconnect the stop light switch assembly connector.

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - IG2 RELAY, BATTERY)

  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

      A55-2 (GND) - Body ground

      Always

      Below 1 Ω

    3. Reconnect the stop light switch assembly connector.

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  3. CHECK ECM (STP AND ST1- VOLTAGE)

    1. U122117E02

      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

      A76-10 (ST1-) - Body ground

      Released

      11 to 14 V

      Depressed

      Below 1.5 V

      A76-9 (STP) - Body ground

      Released

      Below 1.5 V

      Depressed

      11 to 14 V
      Table 2. Text in Illustration

      *a

      Brake Pedal Depressed

      *b

      Brake Pedal Released

      *c

      Front view of wire harness connector

      (to ECM)

    4. Reconnect the ECM connector.

    REPLACE ECM

    (Click here)

  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

      A55-3 (L) - A76-9 (STP)

      Always

      Below 1 Ω

      A55-5 (L) - A76-10 (ST1-)

      Always

      Below 1 Ω

      Standard Resistance (Check for Short)

      Tester Connection

      Condition

      Specified Condition

      A55-3 (L) or A76-9 (STP) - Body ground

      Always

      10 kΩ or higher

      A55-5 (L) or A76-10 (ST1-) - Body ground

      Always

      10 kΩ or higher

    4. Reconnect the stop light switch assembly connector.

    5. Reconnect the ECM connector.

    REPLACE STOP LIGHT SWITCH ASSEMBLY

    (Click here)

    REPAIR OR REPLACE HARNESS OR CONNECTOR