Toyota Tundra. Manual — part 1393

Standard voltage

STANDARD VOLTAGE SPECIFICATION

HINT:

The output voltage should fluctuate up and down, similarly to the diagram, when the wheel is
turned slowly.

Fig. 174: Identifying Combination Meter Connector Terminal

NG : REPLACE COMBINATION METER ASSEMBLY . (See COMBINATION METER ).

OK : Go To Next Step

5. CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - ECM)

a. Disconnect the J28 combination meter connector.

b. Disconnect the A24 ECM connector.

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

Standard resistance

Tester Connection

Switch Condition

Specified Condition

J28-35 (+S) - Body ground



Ignition switch ON



Wheel is turned slowly

Voltage generated intermittently

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

STANDARD RESISTANCE SPECIFICATION

Fig. 175: Identifying A24 ECM & J28 Combination Meter Connectors

NG : REPAIR OR REPLACE HARNESS OR CONNECTOR

OK : REPLACE ECM (See REMOVAL )

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 sets the DTC.

HINT:

The normal conditions are as shown in the table below. The signals can be read using the Techstream.

BRAKE PEDAL CONDITION CHART

Tester Connection

Condition Specified Condition

J28-35 (+S) - A24-13 (SPD)

Always

Below 1 ohms

J28-35 (+S) or A24-13 (SPD) - Body ground Always

10 kohms or higher

Signal

Brake Pedal Released

In Transition

Brake Pedal Depressed

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

DTC DETECTION CONDITION AND TROUBLE AREA

WIRING DIAGRAM

Fig. 176: Brake Switch - Wiring Diagram

INSPECTION PROCEDURE

HINT:



Read freeze frame data using the Techstream. Freeze frame data records the engine condition when

STP

OFF

ON

ON

ST1-

ON

ON

OFF

DTC

Code

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

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

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.



STP signal conditions can be checked using the Techstream.

a. Connect the Techstream to the DLC3.

b. Turn the ignition switch to ON.

c. Turn the Techstream ON.

d. Enter the following menus: Powertrain/Engine and ECT/All Data/Stop Light Switch.

e. Check the STP signal when the brake pedal is depressed and released.

BRAKE PEDAL OPERATION REFERENCE

1. CHECK STOP LIGHT SWITCH ASSEMBLY (B+ VOLTAGE)

a. Disconnect the A4 stop light switch connector.

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

Standard voltage

STANDARD VOLTAGE SPECIFICATION

Fig. 177: Identifying Stop Light Switch Connector Terminal

NG : Go to step 4

Brake Pedal Operation Specified Condition

Depressed

STP signal ON

Released

STP signal OFF

Tester Connection Switch Condition Specified Condition

A4-2 - Body ground

Always

11 to 14 V

A4-3 - Body ground Ignition switch ON

11 to 14 V

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra