Engine Control System

P1520 - Stop Light Switch Signal Malfunction (Only For A/T)

CIRCUIT DESCRIPTION

DTC Detection Condition:

This signal is used to detect when the brakes have been applied. The STP signal voltage is the same as the voltage supplied to the stop lights. The STP signal is used mainly to control the fuel cut-off engine speed.
(The fuel cut-off engine speed is reduced slightly when the vehicle is braking.)

HINT: In this circuit, diagnosis can only be made in the check mode.

Wiring Diagram:

Steps 1 - 2:

Step 3:

INSPECTION PROCEDURE

HINT: Read freeze frame data using the TOYOTA hand-held tester or OBD II scan tool. Because freeze frame records the engine conditions when the malfunction is detected. When troubleshooting it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.

CHECK FOR INTERMITTENT PROBLEMS

TOYOTA hand-held tester only:
By pulling the vehicle's ECM in the check mode, 1 trip detection logic becomes possible instead of 2 trip detection logic and the sensitivity to detect open circuits is increased. This makes it easier to detect intermittent problems.

1. Clear the DTCs.
2. Set the check mode.
3. Perform a simulation test.
4. Check the connector and terminal.
5. Handle the connector.