CRUISE CONTROL SYSTEM, Diagnostic DTC:P0571

DTC Code DTC Name
P0571 Brake Switch "A" Circuit

DESCRIPTION

When the brake pedal is depressed, the stop light switch assembly sends a signal to the ECM. When the ECM receives this signal, it cancels control of vehicle speed by the cruise control system. The fail-safe function operates to enable normal driving even if there is a malfunction in the stop light signal circuit. The cancellation condition occurs when voltage is applied to terminal STP. When the brake is applied, voltage is applied to terminal STP of the ECM through the STOP fuse and the stop light switch assembly, and the ECM cancels control of vehicle speed by the cruise control system.

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).

  • On the GTS, both the Data List items Stop Light Switch Assembly 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. Detection Item DTC Detection Condition Trouble Area
P0571 Brake Switch "A" Circuit When voltage of STP terminal and that of ST1- terminal of ECM are less than 1 V for 0.5 seconds or more.

  • Open or short in stop light switch signal circuit

  • Stop light switch assembly

  • No. 1 integration relay

  • No. 2 integration relay

  • ECM

WIRING DIAGRAM

B002DVHE01

CAUTION / NOTICE / HINT

Note

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

Tech Tips


  • Stop light switch assembly conditions can be checked using the GTS.


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Engine / 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

  • 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.

PROCEDURE


  1. READ VALUE USING GTS (STOP LIGHT SWITCH 1 AND STOP LIGHT SWITCH 2)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG) and turn the GTS on.

    3. Enter the following menus: Powertrain / Cruise Control / Data List.

    4. Read the value displayed on the GTS.


      Powertrain > Cruise Control > Data List
      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      Stop Light Switch 1 Stop light switch signal ON or OFF

      ON: Brake pedal depressed

      OFF: Brake pedal released

      		 -
      Stop Light Switch 2 Stop light switch signal ON or OFF

      ON: Brake pedal depressed

      OFF: Brake pedal released

      		 -

      Powertrain > Cruise Control > Data List
      Tester Display
      Stop Light Switch 1
      Stop Light Switch 2
      OK
      Brake Pedal Operation Stop Light Switch 1 Stop Light Switch 2
      Depressed ON ON
      Released OFF OFF
      Result
      Result Proceed to
      OK (w/ Canister Pump Module) A
      OK (w/o Canister Pump Module) B
      NG C

    A

    CHECK FOR INTERMITTENT PROBLEMS Click here

    B

    CHECK FOR INTERMITTENT PROBLEMS Click here

    C

  2. CHECK TERMINAL VOLTAGE (POWER SOURCE OF STOP LIGHT SWITCH ASSEMBLY)

    B002EZVC01
    *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 Condition Specified Condition
      A3-1 (B) - Body ground Always 11 to 14 V
      Result
      Proceed to
      OK
      NG

    NG

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

    OK

  3. CHECK TERMINAL VOLTAGE (POWER SOURCE OF STOP LIGHT SWITCH ASSEMBLY)

    B002EZVC02
    *a

    Front view of wire harness connector

    (to Stop Light Switch Assembly)

    1. Disconnect the stop light switch assembly connector.

    2. Turn the engine switch on (IG).

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A3-5 (B) - Body ground Engine switch on (IG) 11 to 14 V
      Result
      Proceed to
      OK
      NG

    NG

    CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - NO. 1 INTEGRATION RELAY) Click here

    OK

  4. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - BODY GROUND)


    1. Disconnect the A3 stop light switch assembly connector.

    2. B002EZVC09
      *a

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A3-3 (GND) - Body ground Always Below 1 Ω
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  5. CHECK TERMINAL VOLTAGE (STP AND ST1 - VOLTAGE)

    B002CNBC39
    *a Brake Pedal Depressed
    *b Brake Pedal Released
    *c

    Component with harness connected

    (ECM)

    1. Turn the engine 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
      A12-12 (ST1-) - Body ground Released 7.5 to 14 V
      Depressed Below 1.5 V
      A12-13 (STP) - Body ground Released Below 1.5 V
      Depressed 7.5 to 14 V
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE ECM Click here

    NG

  6. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - ECM - NO. 2 INTEGRATION RELAY)


    1. Disconnect the A3 stop light switch assembly connector.

    2. Disconnect the A12 ECM connector.

    3. Remove the No. 2 integration relay from No. 2 engine room relay block.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A3-4 (L) - A12-12 (ST1-) Always Below 1 Ω
      A3-2 (L) - 2A-11 (STP0) Always Below 1 Ω
      A12-13 (STP) - 2A-5 (STP1) Always Below 1 Ω
      A3-4 (L) or A12-12 (ST1-) - Body ground and other terminals Always 10 kΩ or higher
      A3-2 (L) or 2A-11 (STP0) - Body ground and other terminals Always 10 kΩ or higher
      A12-13 (STP) or 2A-5 (STP1) - Body ground and other terminals Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  7. CHECK TERMINAL VOLTAGE (NO. 2 INTEGRATION RELAY - BODY GROUND)

    B002CFKC01
    *a Brake Pedal Depressed
    *b Brake Pedal Released
    *c

    Front view of wire harness connector

    (to No. 2 Integration Relay)

    1. Remove the No. 2 integration relay from No. 2 engine room relay block.

    2. Turn the engine switch on (IG).

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

      Standard Voltage
      Tester Connection Brake Pedal Operation Specified Condition
      2A-11 (STP0) - Body ground Released 7.5 to 14 V
      Depressed Below 1.5 V
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE NO. 2 INTEGRATION RELAY Click here

    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

  8. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - NO. 1 INTEGRATION RELAY)


    1. Disconnect the A3 stop light switch assembly connector.

    2. Remove the No. 1 integration relay from No. 2 engine room relay block.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A3-5 (B) - 2F-7 Always Below 1 Ω
      A3-5 (B) or 2F-7 - Body ground and other terminals Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  9. CHECK TERMINAL VOLTAGE (POWER SOURCE OF NO. 1 INTEGRATION RELAY)

    B002DJNC01
    *a

    Front view of wire harness connector

    (to No. 1 Integration Relay)

    1. Disconnect the No. 1 integration relay connector.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      2D-1 - Body ground Always 11 to 14 V
      2E-16 - Body ground Always Below 1 Ω
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  10. CHECK TERMINAL VOLTAGE (POWER SOURCE OF NO. 1 INTEGRATION RELAY)

    B002ER6C01
    *a

    Front view of wire harness connector

    (to No. 1 Integration Relay)

    1. Disconnect the No. 1 integration relay connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      2E-16 - Body ground Always Below 1 Ω
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE NO. 1 INTEGRATION RELAY Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR