SFI SYSTEM, Diagnostic DTC:P0571

DTC Code DTC Name
P0571 Brake Switch "A" Circuit

DESCRIPTION

The stop light switch assembly 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 both 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 assembly and stores the DTC.

Tech Tips

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

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 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
P0571

Conditions (a) and (b) continue for 3 seconds or more (1 trip detection logic):


  • (a) Ignition switch ON

  • (b) STP signal off when ST1 signal off

  • Open or short in stop light switch signal circuit

  • Stop light switch assembly

  • ECM

WIRING DIAGRAM

A01VF3AE05
A01VGRFE02

CAUTION / NOTICE / HINT

Note


  • Perform electronic throttle learning after replacing the ECM Click here.

  • 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. Freeze frame data records 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.

  • STP signal conditions can be checked using the intelligent tester.


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

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

    5. Check the STP signal when the brake pedal is depressed and released.

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

PROCEDURE


  1. READ VALUE USING INTELLIGENT TESTER (STOP LIGHT SWITCH))


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

    4. Enter the following menus: Powertrain / Engine and ECT / Stop Light Switch.

    5. Read the value displayed on the tester.

      Standard
      Condition Specified Condition
      Brake pedal depressed STP signal ON
      Brake pedal released STP signal OFF

    OK

    CHECK FOR INTERMITTENT PROBLEMS Click here

    NG

  2. CHECK STOP LIGHT SWITCH ASSEMBLY INSTALLATION


    1. Check the stop light switch assembly installation Click here.

      OK
      Stop light switch assembly is installed correctly.
      Result
      Result Proceed to
      OK (for Bulb Type Stop Light) A
      OK (for LED Type Stop Light) B
      NG C

    B

    CHECK TERMINAL VOLTAGE (STOP LIGHT SWITCH ASSEMBLY) Click here

    C

    SECURELY REINSTALL STOP LIGHT SWITCH ASSEMBLY Click here

    A

  3. CHECK TERMINAL VOLTAGE (STOP LIGHT SWITCH ASSEMBLY)

    A01VKHWE03
    Text in Illustration
    *a

    Front view of wire harness connector

    (to Stop Light Switch Assembly)

    1. Disconnect the stop light switch assembly connector.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A38-2 - Body ground Always 11 to 14 V
      A38-4 - Body ground Ignition switch ON 11 to 14 V

    NG

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

    OK

  4. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. Inspect the stop light switch assembly Click here.


    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

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


    1. Disconnect the A38 stop light switch assembly connector.

    2. Disconnect the A71 ECM connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A38-1 - A71-31 (STP) Always Below 1 Ω
      A38-3 - A71-7 (ST1-) Always Below 1 Ω
      A38-1 or A71-31 (STP) - Body ground Always 10 kΩ or higher
      A38-3 or A71-7 (ST1-) - Body ground Always 10 kΩ or higher

    OK

    REPLACE ECM Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  6. CHECK TERMINAL VOLTAGE (STOP LIGHT SWITCH ASSEMBLY)


    1. Disconnect the stop light switch assembly connector.

    2. A01VJOOE03
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A83-7 (B) - Body ground Always 11 to 14 V
      A83-6 (B) - Body ground Ignition switch ON 11 to 14 V

    NG

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

    OK

  7. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. Inspect the stop light switch assembly Click here.


    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

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


    1. Disconnect the A83 stop light switch assembly connector.

    2. Disconnect the A71 ECM connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A83-3 (L) - A71-31 (STP) Always Below 1 Ω
      A83-5 (L) - A71-7 (ST1-) Always Below 1 Ω
      A83-3 (L) or A71-31 (STP) - Body ground Always 10 kΩ or higher
      A83-5 (L) or A71-7 (ST1-) - Body ground Always 10 kΩ or higher

    OK

    REPLACE ECM Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR