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
–
DIAGNOSTICS
ENGINE
478
WIRING DIAGRAM
–
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
NG
Replace stop light switch.
OK
B17446
Brake Pedal
Depressed
Brake Pedal
Released
ON
( )
( )
ST1– (+)
E4
E6
E1(–)
DI–286
–
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
NG
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