Dtc P0504 Brake Switch A / B Correlation

Engine Hybrid System. Yaris. Ncp93, 131
1Nz-Fe Engine Control. Yaris. Ncp93, 131

DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

CHECK STOP LIGHT SWITCH ASSEMBLY (TERMINAL B VOLTAGE)

INSPECT STOP LIGHT SWITCH ASSEMBLY

INSPECT ECM (STP AND ST1 - VOLTAGE)

INSPECT FUSE (STOP AND IGN FUSE)

DTC P0504 Brake Switch "A" / "B" Correlation


DESCRIPTION

The stop light switch is a duplex system that transmits two signals: STP and ST1-. These two signals are used by the ECM to monitor whether or not the brake system is working properly. If the signals, which indicate the brake pedal is being depressed and released, are detected simultaneously, the ECM interprets this as a malfunction in the stop light switch and stores the DTC.

HINT:
The normal switch conditions are as shown in the table below.

Signal (ECM Terminal)
Brake Pedal Released
In Transition
Brake Pedal Depressed
STP
OFF
ON
ON
ST1-
ON
ON
OFF
  1. [OFF] denotes ground potential.
  2. [ON] denotes battery potential (+B).
  3. On the Techstream, both the Data List items Stop Light Switch and ST1 are ON when the brake pedal is depressed because the ST1 indication characteristic is opposite to the Stop Light Switch indication.

DTC No.
DTC Detection Condition
Trouble Area
P0504
Conditions (a), (b) and (c) continue for 0.5 seconds or more
(1 trip detection logic):
(a) Ignition switch ON
(b) Brake pedal released
(c) STP signal OFF when ST1- signal OFF
  1. Short in stop light switch signal circuit
  2. STOP fuse
  3. IGN fuse
  4. Stop light switch
  5. ECM

WIRING DIAGRAM


Yaris. Ncp93, 131.1Nz-Fe Engine Control.Sfi System (For Sedan). Dtc P0504 Brake Switch A / B Correlation


INSPECTION PROCEDURE

NOTICE:
Inspect the fuses for circuits related to this system before performing the following inspection procedure.
HINT:
  1. Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.
  2. STP signal conditions can be checked using the Techstream.
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine and ECT / Data List / Stop Light Switch.
    5. Check the STP signal when the brake pedal is depressed and released.

Brake Pedal Operation
Stop Light Switch
ST1
Depressed
ON
ON
Released
OFF
OFF
1.CHECK STOP LIGHT SWITCH ASSEMBLY (TERMINAL B VOLTAGE)
Yaris. Ncp93, 131.1Nz-Fe Engine Control.Sfi System (For Sedan). Dtc P0504 Brake Switch A / B Correlation

  1. Disconnect the A13 stop light switch connector.

  1. Turn the ignition switch to ON.

  1. Measure the voltage between the terminals of the A13 stop light switch connector and body ground.

    Standard voltage:
    Tester Connections
    		Specified Conditions
    B (A13-2) - Body ground
    		11 to 14 V
    B (A13-3) - Body ground

  1. Reconnect the stop light switch connector.



NG
Go to step 4
OK


2.INSPECT STOP LIGHT SWITCH ASSEMBLY
Yaris. Ncp93, 131.1Nz-Fe Engine Control.Sfi System (For Sedan). Dtc P0504 Brake Switch A / B Correlation

  1. Remove the stop light switch assembly.

  1. Check the resistance.

    Standard resistance:
    Tester Connections
    		Switch Positions
    		Specified Conditions
    1 - 2
    		Switch pin released
    		Below 1 Ω
    Switch pin pushed in
    		10 kΩ or higher
    3 - 4
    		Switch pin released
    		10 kΩ or higher
    Switch pin pushed in
    		Below 1 Ω

  1. Reinstall the stop light switch assembly.

Result
Result
Proceed to
OK
A
NG
B


B
REPLACE STOP LIGHT SWITCH ASSEMBLY (YARIS_NCP93 RM000001DKT021X.html)
A


3.INSPECT ECM (STP AND ST1 - VOLTAGE)
Yaris. Ncp93, 131.1Nz-Fe Engine Control.Sfi System (For Sedan). Dtc P0504 Brake Switch A / B Correlation

  1. Disconnect the A21 ECM connector.

  1. Turn the ignition switch to ON.

  1. Measure the voltage between the terminals ST1- and STP of the A21 ECM connector and body ground.

    Standard voltage:
    Tester Connections
    		Brake Pedal Operations
    		Specified Conditions
    ST1- (A21-35) - Body ground
    		Released
    		11 to 14 V
    Depressed
    		0 to 3 V
    STP (A21-36) - Body ground
    		Released
    		0 to 3 V
    Depressed
    		11 to 14 V

  1. Reconnect the ECM connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE ECM (YARIS_NCP93 RM000001CN002AX.html)

4.INSPECT FUSE (STOP AND IGN FUSE)
Yaris. Ncp93, 131.1Nz-Fe Engine Control.Sfi System (For Sedan). Dtc P0504 Brake Switch A / B Correlation

  1. Remove the STOP and IGN fuses from the main body ECU.

  1. Check the resistance.

    Standard resistance:
    Below 1 Ω

  1. Reinstall the STOP and IGN fuses.



NG
CHECK FOR SHORTS IN ALL HARNESSES AND CONNECTORS CONNECTED TO FUSE AND REPLACE FUSE
OK

REPAIR OR REPLACE HARNESS OR CONNECTOR