Toyota Tundra Service Manual: Brake Switch "A" / "B" Correlation (P0504)

Toyota Tundra Service Manual / Engine, Hybrid System / 1ur-fe Engine Control / Sfi System / Brake Switch "A" / "B" Correlation (P0504)

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 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

  • [OFF] denotes ground potential.
  • [ON] denotes battery potential (+B).
  • 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

  • Short in stop light switch signal circuit
  • STOP fuse
  • IGN fuse
  • Stop light switch
  • ECM

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses of circuits related to this system before performing the following inspection procedure.

HINT:

  • Read freeze frame data using the Techstream. Freeze frame data records the engine condition when malfunctions are detected. 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.
  • Stop light switch 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 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

PROCEDURE

1.

INSPECT STOP LIGHT SWITCH ASSEMBLY (B+ VOLTAGE)

(a) Disconnect the stop light switch connector.

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

A4-2 - Body ground

Always

11 to 14 V

A4-4 - Body ground

Ignition switch ON

11 to 14 V

NG

GO TO STEP 4

OK

2.

INSPECT STOP LIGHT SWITCH ASSEMBLY

(a) Remove the stop light switch.

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

Standard Resistance:

Tester Connection

Switch Condition

Specified Condition

1 - 2

Pin not pushed

Below 1 Ω

Pin pushed

10 kΩ or higher

3 - 4

Pin not pushed

10 kΩ or higher

Pin pushed

Below 1 Ω

NG

REPLACE STOP LIGHT SWITCH ASSEMBLY

OK

3.

INSPECT ECM (STP AND ST1 - VOLTAGE)

(a) Disconnect the ECM connector.

(b) Turn the ignition switch to ON.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A24-35 (ST1-) - Body ground

Brake pedal released

11 to 14 V

Brake pedal depressed

0 to 3 V

A24-36 (STP) - Body ground

Brake pedal released

0 to 3 V

Brake pedal depressed

11 to 14 V

OK

REPLACE ECM

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

4.

INSPECT FUSES (STOP AND IGN)

(a) Remove the STOP and IGN fuses from the engine room relay block.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

STOP fuse

Always

Below 1 Ω

IGN fuse

Always

Below 1 Ω

OK

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

NG

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

    Vehicle Speed Sensor (P0500)

    Idle Control System (P0505)

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