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 normally 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.

DTC No. DTC Detection Condition Trouble Area
P0571 When voltage of STP terminal and that of ST1- terminal of ECM are less than 1 V for 0.5 sec. or more

  • Stop light switch assembly

  • Stop light switch circuit

  • ECM

WIRING DIAGRAM

A01G46BE01

INSPECTION PROCEDURE

Note

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

PROCEDURE


  1. CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)


    1. A01G768E65
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

      Disconnect the A28 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
      A28-1 (B) - A28-3 (GND) Engine switch off 11 to 14 V
      A28-5 (B) - A28-3 (GND) Engine switch on (IG) 11 to 14 V

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A28-3 (GND) - Body ground Always Below 1 Ω

    4. Reconnect the A28 stop light switch assembly connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  2. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. A01G91LE66
      Text in Illustration
      *a

      Component with harness connected

      (Stop Light Switch Assembly)

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A28-2 (L) - A28-3 (GND) Engine switch off, brake pedal not depressed Below 1 V
      Engine switch off, brake pedal depressed 11 to 14 V
      A28-4 (L) - A28-3 (GND) Engine switch on (IG), brake pedal not depressed 11 to 14 V
      Engine switch on (IG), brake pedal depressed Below 1 V

    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

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


    1. Disconnect the A22 or A64 ECM connector.

    2. Disconnect the A28 stop light switch assembly connector.

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

      Standard Resistance (Check for Open)
      for 2AR-FE
      Tester Connection Condition Specified Condition
      A64-11 (STP) - A28-2 (L) Always Below 1 Ω
      A64-24 (ST1-) - A28-4 (L) Always Below 1 Ω
      for 2GR-FE
      Tester Connection Condition Specified Condition
      A22-51 (STP) - A28-2 (L) Always Below 1 Ω
      A22-36 (ST1-) - A28-4 (L) Always Below 1 Ω
      Standard Resistance (Check for Short)
      for 2AR-FE
      Tester Connection Condition Specified Condition
      A64-11 (STP) or A28-2 (L) - Body ground Always 10 kΩ or higher
      A64-24 (ST1-) or A28-4 (L) - Body ground Always 10 kΩ or higher
      for 2GR-FE
      Tester Connection Condition Specified Condition
      A22-51 (STP) or A28-2 (L) - Body ground Always 10 kΩ or higher
      A22-36 (ST1-) or A28-4 (L) - Body ground Always 10 kΩ or higher
      Result
      Result Proceed to
      OK (for 2AR-FE) A
      OK (for 2GR-FE) B
      NG C

    4. Reconnect the A28 stop light switch assembly connector.

    5. Reconnect the A22 or A64 ECM connector.


    B

    REPLACE ECM Click here

    C

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    A

    REPLACE ECM Click here