SFI SYSTEM, Diagnostic DTC:P0504, P0724

DTC Code DTC Name
P0504 Brake Switch "A" / "B" Correlation
P0724 Brake Switch "B" Circuit High

DESCRIPTION

The stop light switch is a duplex system that transmits 2 signals: STP and ST1-. These 2 signals are used by the ECM to monitor whether or not the brake system is working properly. If the signals, which indicate the brake pedal is being depressed or released, are detected simultaneously, the ECM interprets this as a malfunction in the stop light switch and sets the DTC.

Tech Tips

The normal conditions are as shown in the table below. The signals can be read using the intelligent tester.

Signals 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 intelligent tester, 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) Ignition switch on (IG)

(b) STP signal OFF when ST1- signal OFF

  • Short in stop light switch signal circuit

  • STOP fuse

  • Stop light switch

  • ECM
P0724 The stop light switch remains ON even when the vehicle is driven in a STOP (less than 3 km/h (2 mph)) and GO (30 km/h (19 mph) or more) fashion 5 times. (2 trip detection logic)

  • Short in stop light switch signal circuit

  • Stop light switch

  • ECM

WIRING DIAGRAM

A017E2NE15
A017ERHE16

INSPECTION PROCEDURE

Note

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

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 be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.

  • Stop light switch conditions can be checked using the intelligent tester.


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch on (IG).

    3. Turn the tester on.

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

    5. 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 OPERATION OF STOP LIGHT


    1. Check whether the stop lights turn on and off normally when the brake pedal is depressed and released.

      OK
      Stop lights turn on when brake pedal is depressed.

    NG

    GO TO LIGHTING SYSTEM (STOP LIGHT SYSTEM) Click here

    OK

  2. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. A017D6SE01
      Text in Illustration
      *a

      Component without harness connected

      (Stop Light Switch Assembly)
      *b Free
      *c Pushed In

      Remove the stop light switch assembly.

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

      Standard resistance
      Switch Position Tester Connection Specified Condition
      Switch pin free 1 - 2 Below 1 Ω
      Switch pin free 3 - 4 10 kΩ or higher
      Switch pin pushed in 1 - 2 10 kΩ or higher
      Switch pin pushed in 3 - 4 Below 1 Ω

    3. Reinstall the stop light switch assembly.


    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

  3. READ VALUE USING INTELLIGENT TESTER (STP SIGNAL AND ST1 - VOLTAGE)


    1. A017B72E06
      Text in Illustration
      *a Brake Pedal Depressed
      *b Brake Pedal Released
      *c

      Component with harness connected

      (ECM)

      Turn the ignition switch on (IG).

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

      Standard voltage
      Tester Connection Brake Pedal Operation Specified Condition
      D55-18 (STP) - B48-12 (E1) Depressed 7.5 to 14 V
      D55-18 (STP) - B48-12 (E1) Released Below 1.5 V
      D56-8 (ST1-) - B48-12 (E1) Depressed Below 1.5 V
      D56-8 (ST1-) - B48-12 (E1) Released 7.5 to 14 V

    NG

    CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH - ECM) Click here

    OK

    CHECK FOR INTERMITTENT PROBLEMS Click here

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


    1. Disconnect the stop light switch 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
      A20-1 - D55-18 (STP) Always Below 1 Ω
      A20-3 - D56-8 (ST1-) Always Below 1 Ω
      Check for short
      Tester Connection Condition Specified Condition
      A20-1 or D55-18 (STP) - Body ground Always 10 kΩ or higher
      A20-3 or D56-8 (ST1-) - Body ground Always 10 kΩ or higher

    4. Reconnect the stop light switch connector.

    5. Reconnect the ECM connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH - ECM)

    OK

    REPLACE ECM Click here