DYNAMIC RADAR 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 dynamic radar cruise control. 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 turns the dynamic radar cruise control system off.
The ECM receives the brake demand signal from the driving support ECU assembly and sends it to the skid control ECU (brake actuator assembly). The skid control ECU (brake actuator assembly) receives the signal from the ECM and operates the skid control ECU (brake actuator assembly). The skid control ECU (brake actuator assembly) operates the brake actuator and at the same time illuminates the stop lights by operating the stop light switch assembly (stop light control relay).

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
P0571	Brake Switch "A" Circuit	(Condition 1) Voltage of STP terminal and that of ST1- terminal of ECM are less than 1 V for approximately 0.5 seconds or more. (Condition 2) The ECM detects the stop light switch assembly (stop light control relay) error signal from the skid control ECU (brake actuator assembly) for approximately 0.2 seconds or more while the dynamic radar cruise control is operating.	(Condition 1) Stop light switch assembly Stop light switch circuit ECM (Condition 2) Stop light switch assembly Stop light switch circuit Skid control ECU (brake actuator assembly)

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

P0571

Brake Switch "A" Circuit

(Condition 1)

Voltage of STP terminal and that of ST1- terminal of ECM are less than 1 V for approximately 0.5 seconds or more.

(Condition 2)

The ECM detects the stop light switch assembly (stop light control relay) error signal from the skid control ECU (brake actuator assembly) for approximately 0.2 seconds or more while the dynamic radar cruise control is operating.

(Condition 1)

Stop light switch assembly
Stop light switch circuit
ECM

(Condition 2)

Stop light switch assembly
Stop light switch circuit
Skid control ECU (brake actuator assembly)

WIRING DIAGRAM

INSPECTION PROCEDURE

Note

Inspect the fuses for circuits related to this system before performing the following inspection procedure.
If the ECM is replaced, refer to Registration Click here.

PROCEDURE

CHECK STOP LIGHT OPERATION

Check that the stop lights come on when the brake pedal is depressed, and go off when the brake pedal is released.

Condition	Illumination Condition
Brake pedal depressed	On
Brake pedal released	Off

GO TO LIGHTING SYSTEM (EXT) Click here

READ VALUE USING TECHSTREAM (STOP LIGHT SWITCH1, STOP LIGHT SWITCH2, BRAKE CANCEL SWITCH)

Connect the Techstream to the DLC3.
Turn the engine switch on (IG).
Turn the Techstream on.
Enter the following menus: Powertrain / Radar Cruise / Data List.

Read the Data List according to the display on the Techstream.

Radar Cruise
Tester Display	Measurement Item	Normal Condition	Diagnostic Note
Stop Light Switch 1	Stop light switch signal / ON or OFF	OK: Brake pedal depressed OFF: Brake pedal released	-
Stop Light Switch 2	Stop light switch signal / ON or OFF	OK: Brake pedal depressed OFF: Brake pedal released	-
Brake Cancel Switch	Brake cancel signal / ON or OFF	OK: Brake pedal depressed OFF: Brake pedal released	-

OK
Display changes according to brake pedal operation described in the table.

Turn the engine switch off.

CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - POWER SOURCE) Click here

CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY))

Disconnect the A33 stop light switch assembly connector.
Disconnect the A94 skid control ECU (brake actuator assembly) connector.

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

Standard Resistance (Check for Open)

Tester Connection	Condition	Specified Condition
A33-1 - A94-30 (STP)	Always	Below 1 Ω

Standard Resistance (Check for Short)

Tester Connection	Condition	Specified Condition
A33-1 or A94-30 (STP) - Body ground	Always	10 kΩ or higher

Reconnect the A94 skid control ECU (brake actuator assembly) connector.
Reconnect the A33 stop light switch assembly connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK HARNESS AND CONNECTOR (STOP RELAY - SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY))

Remove the STOP relay.
Disconnect the A94 skid control ECU (brake actuator assembly) connector.

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

Standard Resistance (Check for Open)

Tester Connection	Condition	Specified Condition
Relay terminal 1 - A94-3 (STPO)	Always	Below 1 Ω
Relay terminal 4 - A94-30 (STP)	Always	Below 1 Ω
Relay terminal 3 - A94-22 (STP2)	Always	Below 1 Ω

Standard Resistance (Check for Short)

Tester Connection	Condition	Specified Condition
Relay terminal 1 or A94-3 (STPO) - Body ground	Always	10 kΩ or higher
Relay terminal 4 or A94-30 (STP) - Body ground	Always	10 kΩ or higher
Relay terminal 3 or A94-22 (STP2) - Body ground	Always	10 kΩ or higher

Reinstall the STOP relay.
Reconnect the A94 skid control ECU (brake actuator assembly) connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR

INSPECT STOP RELAY

Remove the STOP relay.

Text in Illustration
*1	STOP Relay

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

Standard Resistance

Tester Connection	Condition	Specified Condition
3 - 4	Battery voltage not applied between terminals 1 and 2	Below 1 Ω
3 - 4	Battery voltage applied between terminals 1 and 2	10 kΩ or higher
3 - 5	Battery voltage not applied between terminals 1 and 2	10 kΩ or higher
3 - 5	Battery voltage applied between terminals 1 and 2	Below 1 Ω

Reinstall the STOP relay.

REPLACE STOP RELAY

REPLACE SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY)
1. Replace the skid control ECU (brake actuator assembly) Click here.
NEXT

CHECK FOR DTCS (DTC P0571)

Connect the Techstream to the DLC3.
Turn the engine switch on (IG).
Clear the DTCs Click here.
Perform the following to make sure that the DTC detection conditions are met.

Tech Tips

If the detection conditions are not met, the malfunction cannot be detected.
1. Drive the vehicle at a speed for which cruise control operation is possible.
2. Turn the dynamic radar cruise control system on using the cruise control main switch (ON-OFF button).
3. Push the cruise control main switch to -SET to activate the dynamic radar cruise control system.
Enter the following menus: Powertrain / Radar Cruise / Trouble Codes.

Check for DTCs.

Result

Result	Proceed to
DTCs are not output	A
DTC P0571 is output (for 2AR-FE)	B
DTC P0571 is output (for 2GR-FE)	C

Turn the engine switch off.

REPLACE ECM Click here

END (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) WAS DEFECTIVE)

CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - POWER SOURCE)

Disconnect the A33 stop light switch assembly connector.

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	Condition	Specified Condition
A33-2 - Body ground	Always	11 to 14 V

Reconnect the A33 stop light switch assembly connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR

INSPECT STOP LIGHT SWITCH ASSEMBLY
1. Remove the stop light switch assembly Click here.
2. Inspect the stop light switch assembly Click here.
NG
REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

OK

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

Disconnect the A33 stop light switch assembly connector.
Disconnect the A25 ECM connector.

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
A33-3 - A25-24 (ST1-)	Always	Below 1 Ω
A33-1 - A25-11 (STP)	Always	Below 1 Ω

for 2GR-FE
Tester Connection	Condition	Specified Condition
A33-3 - A25-36 (ST1-)	Always	Below 1 Ω
A33-1 - A25-51 (STP)	Always	Below 1 Ω

Standard Resistance (Check for Short)

for 2AR-FE
Tester Connection	Condition	Specified Condition
A33-3 or A25-24 (ST1-)- Body ground	Always	10 kΩ or higher
A33-1 or A25-11 (STP) - Body ground	Always	10 kΩ or higher

for 2GR-FE
Tester Connection	Condition	Specified Condition
A33-3 or A25-36 (ST1-) - Body ground	Always	10 kΩ or higher
A33-1 or A25-51 (STP) - Body ground	Always	10 kΩ or higher

Reconnect the A33 stop light switch assembly connector.

Reconnect the A25 ECM connector.

Result

Result	Proceed to
NG	A
OK (for 2AR-FE)	B
OK (for 2GR-FE)	C

REPLACE ECM Click here

REPAIR OR REPLACE HARNESS OR CONNECTOR