Lexus RX300 (MCU15). Service manual - part 220

A02037

ON

ON

STP

Brake Pedal
Depressed

Brake Pedal
Released

(+)

(–)

DI–112

–

DIAGNOSTICS

ENGINE

LEXUS RX300   (RM785E)

OK

2

Check STP signal.

When using hand–held tester:
PREPARATION:
(a)

Connect the hand–held tester to the DLC3.

(b)

Turn the ignition switch ON and push the hand–held tes-
ter main switch ON.

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

Brake Pedal

STP Signal

Depressed

ON

Released

OFF

When not using hand–held tester:
PREPARATION:
Turn the ignition switch ON.
CHECK:
Check the voltage between terminal STP of the engine ECU
connector and body ground.
OK:

Brake Pedal

Voltage

Depressed

7.5 – 14 V

Released

Below 1.5 V

OK

Check for intermittent problems 
(See page DI–3).

NG

3

Check harness and connector between engine ECU and stop light switch 
(See page IN–32).

NG

Repair or replace harness or connector.

OK

Check and replace engine ECU 
(See page IN–32).

A14520

Engine ECU

BATT

E9

1

B–Y

2B

7

EFI

2I

1

Engine Room J/B

Battery

w

1

3

w

FL Block

F11

–

DIAGNOSTICS

ENGINE

DI–113

LEXUS RX300   (RM785E)

DTC

P1600

ECU BATT Malfunction

CIRCUIT DESCRIPTION

Battery positive voltage is supplied to terminal BATT of the engine ECU even when the ignition switch is OFF
for use by the DTC memory and air–fuel ratio adaptive control value memory, etc.

DTC No.

DTC Detecting Condition

Trouble Area

P1600

Open in back up power source circuit

S Open in back up power source circuit

S Engine ECU

HINT:
If DTC P1600 appear, the engine ECU does not store another DTC.

WIRING DIAGRAM

DI1ME–17

A02038

LOCK

BATT

(–)

(+)

I08371

A10578

Engine Room J/B

EFI Fuse

DI–114

–

DIAGNOSTICS

ENGINE

LEXUS RX300   (RM785E)

INSPECTION PROCEDURE

HINT:
Read freeze frame data using hand–held tester. Because freeze frame records the engine conditions when
the malfunction is detected, when troubleshooting it is useful for determining whether the vehicle was run-
ning or stopped, the engine warmed up or not, the air–fuel ratio lean or rich, etc. at the time of the malfunction.

1

Check voltage between terminal BATT of engine ECU connector and body
ground.

PREPARATION:
Remove the engine ECU with connector still connected (See
page FI–70).
CHECK:
Measure voltage between terminal BATT of the engine ECU
connector and body ground.
OK:

Voltage: 9 – 14 V

OK

Check and replace engine ECU (See page
 IN–32).

NG

2

Check EFI fuse of engine room J/B.

PREPARATION:
Remove the EFI fuse from the engine room J/B.
CHECK:
Check continuity of the EFI fuse.
OK:

Continuity

NG

Check for short in all harness and components
connected to EFI fuse.

OK

Check and repair harness or connector be-
tween battery and EFI fuse, and EFI fuse and
engine ECU (See page IN–32).

–

DIAGNOSTICS

ENGINE

DI–115

LEXUS RX300   (RM785E)

DTC

P1645

Body ECU Malfunction

CIRCUIT DESCRIPTION

ECU receives the operating condition (ON/OFF) of A/C from A/C ECU and it also receives the electrical load
information from the body ECU.
ECU uses these information to control the engine (idle up, etc.).

DTC No.

DTC Detecting Condition

Trouble Area

P1645

Condition (a) or (b) continues for 5.0 seconds or more:

(a) No communication from body ECU

(b) No communication from A/C ECU

S Body ECU

S A/C ECU

S Communication bus

INSPECTION PROCEDURE

Perform troubleshooting the Multiplex Communication System (See page DI–683).

DI64J–03