Toyota Sequoia (2005). Manual - part 122

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DIAGNOSTICS

ENGINE

DI–283

477

DTC

P0504

Brake Switch ”A”/”B” Correlation

CIRCUIT DESCRIPTION

In addition to turning on the stop lamps, the stop lamp switch signals are used for a variety of engine, trans-
mission, and suspension functions as well as being an input for diagnostic checks. It is important that the
switch operates properly, therefore this switch is designed with two complementary signal outputs: STP and
ST1–. The ECM analyzes these signal outputs to detect malfunctions in the stop lamp switch.
HINT:
Normal condition is as shown in the table.

Signal

Brake pedal released

In transition

Brake pedal depressed

STP

OFF

ON

ON

ST1–

ON

ON

OFF

DTC No.

DTC Detection Condition

Trouble Area

P0504

Conditions (a), (b) and (c) continue for 0.5 sec. or more:

(a) Ignition switch ON

(b) Brake pedal released

(c) STP signal is OFF when the ST1– signal is OFF

Short in stop lamp switch signal circuit

Stop lamp fuse

Stop lamp switch

ECM

DID8C–01

I18
Ignition 
SW

A23552

ECM

STOP

STP

ALT

Battery

E4

16

G–Y

J/C

1

S14 Stop Light SW

2

G–W

B

R7
Stop
Light
LH

R8
Stop
Light
RH

3

5

8

W–R

A

W

High 
Mounted
Stop Light

W–B

1L 1

1F

7

F10
Fusible
Link
Block

Instrument 
Panel J/B

1

4E

G–Y

4

B8
Brake Inhibit Relay

G–Y

4

See VSC System

2

W

J19
J/C

B

C

IC

C

C

C

4

BD1

1

2

2

1

H9

H9

(*1)

(*2)

(*1)

(*2)

BD2

12

J/C

A

1

4

G–W

IG2

*1: w/o Rear Spoiler

*2: w/ Rear Spoiler

AM2

To Towing
Converter Relay

W–B

ST1–

E4

15

4C

4A

1

1

3

L–B

Sub J/B No.4

2

IGN1

B–O

2

4D

2

4A

1E 17

2

1C

1

A

J44

J11

J/C

J10

J

J33

J34

C

3

IJ

5

2C

2D

1

1

AM2

B

W–R

B–R

6

Instrument 
Panel J/B

BP

1

4

G–W

B–O

G–W

G–W

G–W

Sub J/B No.4

J10

J45

4

BJ

J57
J/C

A

W–B

W–B

G–W

High 
Mounted
Stop Light

G–W

J20
J/C

G–W

H

Engine Room
J/B

DI–284

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DIAGNOSTICS

ENGINE

478

WIRING DIAGRAM

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DIAGNOSTICS

ENGINE

DI–285

479

INSPECTION PROCEDURE

HINT:
Read freeze frame data using 

the hand−held tester

. Freeze frame data records the engine conditions when

a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was
running or stopped, if the engine was warmed up or not, if the air–fuel ratio was lean or rich, as well as other
data from the time when a malfunction occurred.

1

Check operation of stop light.

CHECK:
Check if the stop lights come on and go off normally when the brake pedal is operated and released.

NG

Check and repair stop light circuit.

OK

2

Check stop light switch (See page 

BE–47

).

NG

Replace stop light switch.

OK

B17446

Brake Pedal
Depressed

Brake Pedal
Released

ON

( )

( )

ST1– (+)

E4

E6

E1(–)

DI–286

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DIAGNOSTICS

ENGINE

480

3

Check STP signal and ST1– voltage.

PREPARATION:
(a)

Connect the hand–held tester to the DLC3.

(b)

Turn the ignition switch ON.

(c)

Select the item ”DIAGNOSIS / ENHANCED OBD II /
DATA LIST / ALL / STOP LIGHT SW”.

CHECK:
Read the signal displayed on the hand–held tester.
OK:

Standard:

Brake Pedal

Specified Condition

Depressed

STP Signal ON

Released

STP Signal OFF

CHECK:
Measure the voltage between the specified terminals of the E4
and E6 ECM connectors.
OK:

Standard:

Tester Connection

Brake Pedal

Specified Condition

ST1– (E4–12) – 

E1 (E6–1)

Depressed

Below 1.5 V

ST1– (E4–12) – 

E1 (E6–1)

Released

7.5 to 14 V

OK

Check for intermittent problems (See page 

DI–11

).

NG