Lexus RX300 (MCU15). Manual — part 228

DI84I–01

FI6907

D09456

Hand–held Tester

DLC3

DI–144

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DIAGNOSTICS

AUTOMATIC TRANSAXLE

LEXUS RX300 (RM785E)

PRE–CHECK

1.

DIAGNOSIS SYSTEM

(a)

Description for EURO–OBD

S

When troubleshooting Euro–OBD vehicles, the
only difference from the usual troubleshooting pro-
cedure is that you connect to the vehicle the OBD
scan tool complying with ISO 15031–4 or hand–
held tester, and read off various data output from
the vehicle’s engine ECU.
Euro–OBD regulations require that the vehicle’s
on–board computer lights up the check engine
warning ignition the instrument panel when the
computer detects a malfunction in the emission
control system/components or in the power–train
control components which affect vehicle emissions,
or a malfunction in the computer. In addition to the
check engine warning light (CHK ENG) lighting up
when a malfunction is detected, the applicable
Diagnostic Trouble Codes (DTCs) prescribed by
ISO15031–6 are recorded in the engine ECU
memory (See page DI–14). If the malfunction does
not repaired in 3 consecutive trips, the (CHK ENG)
goes off automatically but the DTCs remain re-
corded in the engine ECU memory.

S

To check the DTCs, connect the OBD scan tool or
hand–held tester to the Data Link Connector 3
(DLC3) on the vehicle. The OBD scan tool or hand–
held tester also enables you to erase the DTCs and
check freezed frame data and various forms of en-
gine data (For operating instructions, see the OBD
scan tool’s instruction book.).
DTCs include ISO controlled codes and manufac-
turer controlled codes. ISO controlled codes must
be set as prescribed by the ISO, while manufacturer
controlled codes can be set freely by the manufac-
turer within the prescribed limits (See DTC chart on
page DI–155).

N09214

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DIAGNOSTICS

AUTOMATIC TRANSAXLE

DI–145

LEXUS RX300 (RM785E)

S

The diagnosis system operates in normal mode
during normal vehicle use. It also has a check mode
for technicians to simulate malfunction symptoms
and troubleshoot. Most DTCs use 2 trip detection
logic* to prevent erroneous detection, and ensure
thorough malfunction detection. By switching the
engine ECU to check mode when troubleshooting,
the technician can cause the check engine warning
light to light up for a malfunction that is only detected
once or momentarily (Hand–held tester only) (See
step 2).

S

*2 trip detection logic:
When a malfunction is first detected, the malfunc-
tion is temporarily stored in the engine ECU
memory (1st trip). If the same malfunction is de-
tected again during the second drive test, this se-
cond detection causes the (CHK ENG) to light up
(2nd trip).
(However, the ignition switch must be turned OFF
between the 1st trip and the 2nd trip.)

(b)

Check the DLC3.
The vehicle’s engine ECU uses the ISO 9141–2 commu-
nication protocol. The terminal arrangement of DLC3
complies with ISO 15031–3 and matches the ISO 9141–2
format.

Tester connection

Condition

Specified condition

7 (Bus ę Line) – 5 (Signal ground)

During communication

Pulse generation

4 (Chassis Ground) – Body

Always

1 Ω or less

5 (Signal Ground) – Body

Always

1 Ω or less

16 (B+) – Body

Always

9 – 14 V

HINT:
If your display shows UNABLE TO CONNECT TO VEHICLE
when you have connected the cable of the OBD scan tool or
hand–held tester to the DLC3, turned the ignition switch ON
and operated the scan tool, there is a problem on the vehicle
side or tool side.

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

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If communication is still not possible when the tool is con-
nected to another vehicle, the problem is probably in the
tool itself, so consult the Service Department listed in the
tool’s instruction manual.

DI–146

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DIAGNOSTICS

AUTOMATIC TRANSAXLE

LEXUS RX300 (RM785E)

2.

INSPECT DIAGNOSIS (Normal Mode)

(a)

Check the CHK ENG.
(1)

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

HINT:
If the CHK ENG does not light up, troubleshoot the combination
meter (See page BE–68).

(2)

When the engine is started, the CHK ENG should
go off. If the light remains on, the diagnosis system
has detected a malfunction or abnormality in the
system.

(b)

Check the DTC using hand–held tester.

NOTICE:
Hand–held tester only:
When the diagnosis system is switched from normal mode
to check mode, it erases all DTCs and freezed frame data
recorded in normal mode. So before switching modes, al-
ways check the DTCs and freezed frame data, and note
them down.

(1)

Prepare the hand–held tester.

(2)

Connect the hand–held tester to DLC3.

(3)

Turn the ignition switch ON and push the hand–held
tester main switch ON.

(4)

Use the hand–held tester to check the DTCs and
freezed frame data, note them down (For operating
instructions, see the hand–held tester instruction
book.).

(5)

See page DI–155 to confirm the details of the
DTCs.

NOTICE:

S

When simulating symptoms with out a hand–held tes-
ter to check the DTCs, use normal mode. For code on
the DTC chart subject to ”2 trip detection logic”, turn
the ignition switch OFF after the symptom is simu-
lated the first time. Then repeat the simulation pro-
cess again. When the problem has been simulated
twice, the CHK ENG is indicated on the instrument
panel and the DTCs are recorded in the engine ECU.

S

Check the 1st trip DTC using Mode 7 for ISO 15031
(Continuous Test Results of Euro–OBD function in
hand–held tester).

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DIAGNOSTICS

AUTOMATIC TRANSAXLE

DI–147

LEXUS RX300 (RM785E)

3.

INSPECT DIAGNOSIS (Check (Test) Mode)

HINT:
Hand–held tester only:
Compared to the normal mode, the check mode has an in-
creased sensitivity to detect malfunctions.
Furthermore, the same diagnostic items which are detected in
the normal mode can also be detected in the check (test) mode.
(a)

Check the DTC.
(1)

Initial conditions

S

Battery voltage 11 V or more

S

Throttle valve fully closed.

S

Transmission in P or N range

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A/C switched OFF

(2)

Turn the ignition switch OFF.

(3)

Prepare the hand–held tester.

(4)

Connect the hand–held tester to the DLC3.

(5)

Turn the ignition switch ON and push the hand–held
tester main switch ON.

(6)

Switch the hand–held tester from the normal mode
to the check (test) mode.

NOTICE:
If the hand–held tester switches the engine ECU from nor-
mal mode to check mode or vice–versa, or if the ignition
switch is turned from ON to ACC or OFF during check
mode, the DTCs and freezed frame data will be erased.

(7)

Start the engine.

(8)

Simulate the conditions of the malfunction de-
scribed by the customer.

NOTICE:
Leave the ignition switch ON until you have checked the
DTCs, etc.

(9)

After simulating the malfunction conditions, use the
hand–held tester diagnosis selector to check the
DTCs and freezed frame data, etc.

HINT:
Take care not to turn the ignition switch OFF. Turning the ignition
switch OFF switches the diagnosis system from check (test)
mode to normal mode. so all DTCs, etc. are erased.

(10) After checking the DTC, inspect the applicable cir-

cuit.

(b)

Clear the DTC.
The DTCs and freezed frame data will be erased by either
actions.
(1)

Operating the hand–held tester to erase the codes
(See the hand–held tester’s instruction book for op-
erating instructions.).

(2)

Disconnecting the battery terminals of EFI and
ECTS fuses.