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

for Preparation Click here


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 sets the DTC.

HINT:
The normal signal 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 intelligent tester, 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 light switch assembly
  3. STOP fuse
  4. IGN fuse
  5. ECM

WIRING DIAGRAM


A201214E02


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 an intelligent tester. 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. Stop light switch conditions can be checked using the intelligent tester.
    1. Connect the intelligent tester to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the tester on.
    4. Enter the following menus: Powertrain / Engine and ECT / Data List / Stop Light Switch and ST1.
    5. Check the Data List indication when the brake pedal is depressed and released.

      Brake Pedal Operation
      		Stop Light Switch
      		ST1
      Depressed
      		ON
      		ON
      Released
      		OFF
      		OFF

1.INSPECT STOP LIGHT SWITCH ASSEMBLY (TERMINAL VOLTAGE)


    A200909E01

  1. Disconnect the stop light switch assembly connector.

  1. Turn the ignition switch to ON.

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

    Standard Voltage:
    Tester Connection
    		Switch Condition
    		Specified Condition
    A27-2 - Body ground
    		Always
    		11 to 14 V
    A27-3 - Body ground
    		Ignition switch ON
    		11 to 14 V

    Text in Illustration 
    *1
    		Front view of wire harness connector:
    (to Stop Light Switch Assembly)

  1. Reconnect the stop light switch assembly connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - STOP LIGHT SWITCH ASSEMBLY)
OK


2.INSPECT STOP LIGHT SWITCH ASSEMBLY


    A115657E28

  1. Remove the stop light assembly switch.

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

    Standard Resistance:
    Tester Connection
    		Switch Condition
    		Specified Condition
    1 - 2
    		Switch pin not pushed
    		Below 1 Ω
    Switch pin pushed
    		10 kΩ or higher
    3 - 4
    		Switch pin not pushed
    		10 kΩ or higher
    Switch pin pushed
    		Below 1 Ω

    Text in Illustration 
    *1
    		Component without harness connected
    (Stop Light Switch)
    *2
    		Not pushed
    *3
    		Pushed

  1. Reinstall the stop light switch assembly.



NG
REPLACE STOP LIGHT SWITCH ASSEMBLY
OK


3.INSPECT ECM (STP AND ST1 - VOLTAGE)


    A112585E82

  1. Disconnect the ECM connector.

  1. Turn the ignition switch to ON.

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

    Standard Voltage:
    Tester Connection
    		Brake Pedal Operation
    		Specified Condition
    A18-35 (ST1-) - Body ground
    		Released
    		11 to 14 V
    Depressed
    		Below 1.5 V
    A18-36 (STP) - Body ground
    		Released
    		Below 1.5 V
    Depressed
    		11 to 14 V

    Text in Illustration 
    *1
    		Brake Pedal Depressed
    *2
    		Brake Pedal Released
    *3
    		Front view of wire harness connector
    (to ECM)

  1. Reconnect the ECM connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE ECM (Click here)