Toyota Sequoia (2005). Manual - part 59

A23656

0.2 V/DIV

200 msec./DIV

Ground

A23657

10 msec./DIV

5 V/DIV

Ground

–

DIAGNOSTICS

ENGINE

DI–39

233

WAVEFORM 10
Heated oxygen sensor

ECM Terminal Names

Between OX1B and E2

Tester Ranges

0.2 V/DIV, 200 msec./DIV

Conditions

Engine speed maintained 2,500 rpm for 2 minutes after

warming up sensor

HINT:
In the DATA LIST, item O2S B1S2 shows the ECM input values
from the heated oxygen sensor.

WAVEFORM 11
Engine speed signal

ECM Terminal Names

Between TACH and E1

Tester Ranges

5 V/DIV, 10 msec./DIV

Conditions

Idling

HINT:
The wavelength becomes shorter as vehicle speed increases.

DID7X–01

FI0534

D13872

Hand–Held Tester

DLC3

DI–40

–

DIAGNOSTICS

ENGINE

234

DIAGNOSIS SYSTEM

1.

Description

When troubleshooting On–Board Diagnostic (OBD ll) ve-
hicles, the vehicle must be connected to the hand–held
tester. Various data output from the vehicle’s ECM can
then be read.

OBD ll regulations require that the vehicle’s on–board
computer illuminates the Malfunction Indicator Light (MIL)
on the instrument panel when the computer detects a
malfunction in: 1) the emission control system/compo-
nents, or 2) the powertrain control components (which af-
fect vehicle emissions), or 3) the computer. In addition,
the applicable Diagnostic Trouble Codes (DTCs) pre-
scribed by SAE J2012 are recorded in the ECM memory
(See page 

DI–58

).

If the malfunction does not reoccur in 3 consecutive

 

trips, the

MIL goes off automatically but the DTCs remain recorded in the
ECM memory.
To check the DTC, connect the hand–held tester or OBD II scan
tool to the Data Link Connector 3 (DLC3) of the vehicle. The
hand–held tester or OBD II scan tool also enables you to erase
the DTC and check the freeze frame data and various forms of
engine data (See the instruction manual for the hand–held tes-
ter). The DTC includes SAE controlled codes and manufacturer
controlled codes. SAE controlled codes must be set according
to the SAE, while manufacturer controlled codes can be set by
a manufacturer with certain restrictions (See the DTC chart on
page 

DI–58

).

2.

NORMAL MODE AND CHECK MODE

The diagnosis system operates in ”normal mode” during normal
vehicle use. In ”normal mode”, 2 trip detection logic* is used to
ensure accurate detection of malfunctions. A ”check mode” is
also available to technicians as an option. In ”check mode”, 1
trip detection logic is used for simulating malfunction symptoms
and increasing the system’s ability to detect malfunctions, in-
cluding intermittent malfunctions (See page 

DI–11

).

3.

2–TRIP DETECTION LOGIC

When a malfunction is first detected, the malfunction is tempo-
rarily stored in the ECM memory. This is known as 1st trip detec-
tion. If the ignition switch is turned OFF and then ON again, and
the same malfunction is detected again, the MIL will illuminate.
This is known as 2nd trip detection.

A04550

1 2 3 4 5 6 7 8

11 12 13 14 15 16

9 10

DLC3

–

DIAGNOSTICS

ENGINE

DI–41

235

Freeze frame data:
The freeze frame data records the engine conditions (fuel
system, calculated load, engine coolant temperature, fuel
trim, engine speed, vehicle speed, etc.) when a malfunc-
tion 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.

Priorities for troubleshooting:
When multiple DTCs occur, find out the order in which the DTCs
should be inspected by checking the component’s DTC chart.
If no instructions are written in the DTC chart, check DTCs in the
following order of priority:
(a)

DTCs other than fuel trim malfunction DTCs (P0171,
P0172, P0174 and P0175) and misfire DTCs (P0300 to
P0308).

(b)

Fuel trim malfunction DTCs (P0171, P0172, P0174 and
P0175).

(c)

Misfire DTCs (P0300 to P0308).

4.

CHECK DLC3
The vehicle’s ECM uses the ISO 9141–2 for communica-
tion protocol. The terminal arrangement of the DLC3 com-
plies with SAE J1962 and matches the ISO 9141–2 for-
mat.

Symbol

Terminal Description

Condition

Specified Condition

SIL (7) – SG (5)

Bus ”+” line

During transmission

Pulse generation

CG (4) – Body ground

Chassis ground

Always

Below 1 

Ω

SG (5) – Body ground

Signal ground

Always

Below 1 

Ω

BAT (16) – Body ground

Battery positive

Always

11 to 14 V

CANH (6) – CANL (14)

HIGH–level CAN bus line

Ignition switch OFF

54 to 69 

Ω

CANH (6) – Battery positive

HIGH–level CAN bus line

Ignition switch OFF

1 M

Ω

 or higher

CANH (6) – CG (4)

HIGH–level CAN bus line

Ignition switch OFF

1 k

Ω

 or higher

CANL (14) – Battery positive

LOW–level CAN bus line

Ignition switch OFF

1 M

Ω

 or higher

CANL (6) – CG (4)

LOW–level CAN bus line

Ignition switch OFF

1 k

Ω

 or higher

HINT:
Connect the cable of the hand–held tester to the DLC3, turn the
ignition switch ON and attempt to use the hand–held tester. If
the screen displays UNABLE TO CONNECT TO VEHICLE, a
problem exists in the vehicle side or the tester side.

If the communication is normal when the tool is connected
to another vehicle, inspect the DLC3 on the original ve-
hicle.

DI–42

–

DIAGNOSTICS

ENGINE

236

If the communication is still impossible when the tool is
connected to another vehicle, the problem is probably in
the tool itself, so consult the Service  Department listed in
the tool’s instruction manual.

5.

INSPECT BATTERY VOLTAGE
Battery Voltage: 11 to 14 V

If voltage is below 11 V, recharge the battery before proceeding.
6.

CHECK MIL

(a)

The MIL comes on when the ignition switch is turned ON
and the engine is not running.

HINT:
If the MIL is not illuminated, troubleshoot the MIL circuit (See
page 

DI–512

).

(b)

When the engine is started, the MIL should not illuminate.
If the lamp remains on, the diagnosis system has de-
tected a malfunction or abnormality in the system.

7.

ALL READINESS

For this vehicle, using the hand–held tester allows readiness
codes corresponding to all DTCs to be read. When diagnosis
(normal or malfunctioning) has been complete, readiness
codes are set. Enter the following menus: ENHANCED OBD II
/ MONITOR STATUS on the hand–held tester.