Engine Control System

DTC P1520 Stop Light Switch Signal Malfunction

CIRCUIT DESCRIPTION

DTC Detecting 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 while the vehicle is braking.)

Wiring Diagram:

Step 1:

Step 1 (Continued) - 3:

INSPECTION PROCEDURE

CHECK FOR INTERMITTENT PROBLEMS

LEXUS hand-held tester only:
By putting the vehicle's ECM in the check mode, 1 trip detection logic is possible instead of 2 trip detection logic and 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. Check the connector connection.