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 outputs a signal to the ECM. When the ECM receives the signal, it cancels control of vehicle speed by the cruise control system. The fail-safe function operates to enable normal operation 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 pedal is depressed, voltage is applied to terminal STP of the ECM through the STOP fuse and the stop light switch assembly, and the ECM turns the cruise control system off.

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.

  • Stop light switch assembly

  • Harness or connector

  • ECM

WIRING DIAGRAM

B000WSDE02

CAUTION / NOTICE / HINT

Note


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

  • After turning the engine switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.

    Click here

PROCEDURE


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


    1. B000USTC18
      *a

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

      Disconnect the A4 stop light switch assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A4-3 (GND) - Body ground Always Below 1 Ω

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A4-1 (B) - Body ground Always 11 to 14 V
      A4-5 (B) - Body ground Engine switch on (IG) 11 to 14 V
      A4-5 (B) - Body ground Engine switch off Below 1 V

    4. Connect the A4 stop light switch assembly connector.

      Result
      Proceed to
      OK
      NG

    NG

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

    OK

  2. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. Inspect the stop light switch assembly.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

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


    1. Disconnect the cable from the negative (-) battery terminal.

    2. Disconnect the A58 ECM connector.

    3. Disconnect the A4 stop light switch assembly connector.

    4. Disconnect the A10 skid control ECU assembly connector.

    5. Disconnect the P75 shift control ECU connector.

    6. Disconnect the X99 No. 3 semiconductor power integration ECU connector.

    7. Disconnect the X23 certification ECU (smart key ECU assembly) connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A58-28 (ST1-) - A4-4 (L) Always Below 1 Ω
      A58-27 (STP) - A4-2 (L) Always Below 1 Ω
      A58-28 (ST1-) or A4-4 (L) - Body ground Always 10 kΩ or higher
      A58-27 (STP) or A4-2 (L) - Body ground Always 10 kΩ or higher

    9. Connect the X23 certification ECU (smart key ECU assembly) connector.

    10. Connect the X99 No. 3 semiconductor power integration ECU connector.

    11. Connect the P75 shift control ECU connector.

    12. Connect the A10 skid control ECU assembly connector.

    13. Connect the A4 stop light switch assembly connector.

    14. Connect the A58 ECM connector.

    15. Connect the cable from the negative (-) battery terminal.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE ECM Click here

    NG

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