Dtc P0571 Stop Light Switch Circuit Malfunction
DESCRIPTION
WIRING DIAGRAM
INSPECTION PROCEDURE
READ VALUE USING DATA LIST (STOP LIGHT SWITCH)
INSPECT FUSE (STOP, IGN)
INSPECT STOP LIGHT SWITCH
CHECK WIRE HARNESS (STOP LIGHT SWITCH - BODY GROUND)
CHECK ECM (STP, ST1- VOLTAGE)
DTC P0571 Stop Light Switch Circuit Malfunction |
DESCRIPTION
While driving with the cruise control, if the ECM detects that the brake pedal is depressed, the cruise control operation will be canceled. The stop light switch sends brake pedal status signals to the ECM. When the brake pedal is not depressed, terminal ST1- is equal to the positive (+) battery voltage and terminal STP is below 1 V. When the brake pedal is depressed, the ECM cancels cruise control operation. The ECM outputs this DTC when the voltage of terminals ST1- and STP are both below 1 V for 0.5 seconds or more at the same time. The fail-safe function operates to enable normal driving even if there is a malfunction in the stop light signal circuit.DTC No.
| DTC Detection Condition
| Trouble Area
|
P0571
| ECM detects malfunction of stop light switch circuit under both of following conditions:
- Voltage of terminal STP is less than 1 V for 0.5 sec. or more
- Voltage of terminal ST- is less than 1 V for 0.5 sec. or more
| - Stop light switch
- Stop light switch circuit
- ECM
|
WIRING DIAGRAM
INSPECTION PROCEDURE
| 1.READ VALUE USING DATA LIST (STOP LIGHT SWITCH) |
Connect the intelligent tester to the DLC3.
Turn the ignition switch ON, and turn the intelligent tester main switch ON.
Check the Data List for proper functioning of the stop light switch.
ECM (Cruise control):Item
| Measurement Item / Display (Range)
| Normal Condition
| Diagnostic Note
|
Stop Light SW M-CPU
| Stop light switch signal (Main CPU) / ON or OFF
| ON: Brake pedal is depressed
OFF: Brake pedal is released
| -
|
Stop Light SW1 S-CPU
| Stop light switch signal (Sub CPU) / ON or OFF
| ON: Brake pedal is depressed
OFF: Brake pedal is released
| -
|
Stop Light SW2 S-CPU
| Stop light switch signal (Sub CPU) / ON or OFF
| ON: Brake pedal is depressed
OFF: Brake pedal is released
| -
|
- OK:
- Display changes according to brake pedal operation described in above table.
- HINT:
- Stop light SW1 indicates the input of the ST1- terminal, and stop light SW2 indicates the input of the STP terminal.
| 2.INSPECT FUSE (STOP, IGN) |
Remove the STOP and IGN fuses from the instrument panel junction block.
Measure the resistance of the fuses.
- Standard resistance:
- Below 1 Ω
| 3.INSPECT STOP LIGHT SWITCH |
Disconnect the S14 stop light switch connector.
Measure the resistance of the switch.
- Standard resistance:
Tester Connection
| Switch Condition
| Specified Condition
|
1 - 2
| Not pushed
| Below 1 Ω
|
3 - 4
| Not pushed
| 10 kΩ or higher
|
1 - 2
| Pushed
| 10 kΩ or higher
|
3 - 4
| Pushed
| Below 1 Ω
|
| | REPLACE STOP LIGHT SWITCH ASSEMBLY |
|
|
| 4.CHECK WIRE HARNESS (STOP LIGHT SWITCH - BODY GROUND) |
Measure the voltage of the wire harness side connector.
- Standard voltage:
Tester Connection
| Condition
| Specified Condition
|
S14-2 - Body ground
| Always
| 10 to 14 V
|
S14-3 - Body ground
| Ignition switch ON
| 10 to 14 V
|
| | REPAIR OR REPLACE HARNESS AND CONNECTOR |
|
|
| 5.CHECK ECM (STP, ST1- VOLTAGE) |
Reconnect the S14 stop light switch connector.
Disconnect the E14 connector from the ECM.
Turn the ignition switch ON.
Measure the voltage of the wire harness side connector.
- Standard voltage:
Tester Connection
| Brake Pedal Condition
| Specified Condition
|
E14-15 (STP) - Body ground
| Depressed
| 10 to 14 V
|
E14-15 (STP) - Body ground
| Released
| Below 1 V
|
E14-16 (ST1-) - Body ground
| Depressed
| Below 1 V
|
E14-16 (ST1-) - Body ground
| Released
| 10 to 14 V
|
| | REPAIR OR REPLACE HARNESS AND CONNECTOR |
|
|
