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 the cruise control. The fail-safe function operates to enable normal driving even if there is a malfunction in the stop light signal circuit. Cruise control cancellation occurs when voltage is applied to terminal STP. When the brake is applied, voltage is normally applied to terminal STP of the ECM through the STOP fuse and the stop light switch assembly, and the ECM turns the cruise control off.

DTC DTC Detection Condition Trouble Area
P0571 Voltage of STP signal and that of ST1- signal of ECM are less than 1 V for 0.5 seconds or more

  • Stop light switch assembly

  • Stop light switch circuit

  • ECM

WIRING DIAGRAM

A01ELLNE02
A01ELZUE02

INSPECTION PROCEDURE

Tech Tips

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

PROCEDURE


  1. INSPECT STOP LIGHT SWITCH ASSEMBLY (POWER SOURCE)


    1. A01EKAKE01
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

      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
      A35-2 - Body ground Always 11 to 14 V

    3. Reconnect the stop light switch assembly connector.


    NG

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

    OK

  2. INSPECT STOP LIGHT SWITCH ASSEMBLY (POWER SOURCE)


    1. A01EKAKE01
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

      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
      A35-4 - Body ground Ignition switch ON 11 to 14 V

    4. Reconnect the stop light switch assembly connector.


    NG

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

    OK

  3. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. Inspect the stop light switch assembly Click here.


    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

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


    1. A01EL5VE04
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Stop Light Switch Assembly)
      *2

      Front view of wire harness connector

      (to ECM)

      Disconnect the ECM connector.

    2. Disconnect the stop light switch assembly connector.

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

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      A49-29 (STP) - A35-1 Always Below 1 Ω
      A49-39 (ST1-) - A35-3 Always Below 1 Ω
      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      A49-29 (STP) or A35-1 - Body ground Always 10 kΩ or higher
      A49-39 (ST1-) or A35-3 - Body ground Always 10 kΩ or higher

    4. Reconnect the stop light switch assembly connector.

    5. Reconnect the ECM connector.

      Result
      Result Proceed to
      NG A
      OK B

    B

    REPLACE ECM Click here

    A

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