Lexus RX300 (MCU15). Manual - part 209

A11663

VV1, VV2 and NE Signal Waveforms

20 msec./Division (Idling)

VV1

VV2

NE

2V
/Division

GND

GND

GND

DI–68

–

DIAGNOSTICS

ENGINE

LEXUS RX300   (RM785E)

1

Check resistance of crankshaft position sensor (See page IG–14).

Reference: INSPECTION USING OSCILLOSCOPE
During cranking or idling, check between terminals VV1 and
NE–, VV2 and NE–, NE+ and NE– of engine ECU.
HINT:
The correct waveforms are as shown.

NG

 Replace crankshaft position sensor.

OK

2

Check for open and short in harness and connector between engine ECU and 
crankshaft position sensor (See page IN–32).

NG

 Repair or replace harness or connector.

OK

3

Inspect sensor installation and teeth of signal plate.

NG

 Tighten the sensor. Replace signal plate.

OK

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

–

DIAGNOSTICS

ENGINE

DI–69

LEXUS RX300   (RM785E)

DTC

P0340

Camshaft Position Sensor Circuit
Malfunction

CIRCUIT DESCRIPTION

Camshaft position sensor (G(VV) signal) consist of a signal plate and pick up coil. The G(VV) signal plate
has one tooth on its outer circumference and is mounted on the camshaft.
When the camshafts rotate, the protrusion on the signal plate and the air gap on the pick up coil change,
causing fluctuations in the magnetic field and generating an electromotive force in the pick up coil.
The NE signal plate has 34 teeth and is mounted on the crankshaft. The NE signal sensor generates 34
signals for every engine revolution. The engine ECU detects the standard crankshaft angle based on the
G2+ signals and the actual crankshaft angle and the engine speed by the NE signals.

DTC No.

DTC Detecting Condition

Trouble Area

P0340

No camshaft position sensor signal to engine ECU during

cranking

S Open or short in camshaft position sensor circuit

S Camshaft position sensor

P0340

S Starter

Open in NE circuit

S Starter

Open in NE– circuit

S Engine ECU

O en in NE  circuit

S Engine ECU

WIRING DIAGRAM

Refer to DTC P0335 on page DI–67.

INSPECTION PROCEDURE

HINT:
Read freed 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 resistance of camshaft position sensor (Signal generator) 
(See page IG–1).

Refer to DTC P0335 on page DI–67.

NG

 Replace camshaft position sensor.

OK

2

Check for open and short in harness and connector between engine ECU and
camshaft position sensor (See page IN–32).

NG

 Repair or replace harness or connector.

OK

DI84C–01

DI–70

–

DIAGNOSTICS

ENGINE

LEXUS RX300   (RM785E)

3

Inspect sensor installation.

NG

 Tighten the sensor.

OK

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

A01674

Waveform of A/F Sensor

Normal Catalyst

Abnormal Catalyst

Waveform of Oxygen Sensor
Behind Catalyst

–

DIAGNOSTICS

ENGINE

DI–71

LEXUS RX300   (RM785E)

DTC

P0420

Catalyst System Efficiency Below Threshold

CIRCUIT DESCRIPTION

The engine ECU observes the waveform of the oxygen sensor located behind the catalyst to determine
whether the catalyst is performance has deteriorated.
If the catalyst is performance functioning normally, the waveform of the oxygen sensor located behind the
catalyst switches back and forth between rich and lean much more slowly.
When the waveform of the oxygen sensor located behind the catalyst alternates flatteringly between rich
and lean, it indicates that catalyst performance has deteriorated.

DTC No.

DTC Detecting Condition

Trouble Area

P0420

After the engine and the catalyst are warmed up, and while the

vehicle is driven within the set vehicle and engine speed range,

the waveforms of the heated oxygen sensors (bank 1 sensor

2) have the same amplitude (2 trip detection logic)

S Three–way catalytic converter

S Open or short in oxygen sensor (bank 1 sensor 2) circuit

S Oxygen sensor (bank 1 sensor 2)

S Open or short in A/F sensor (bank 1, 2 sensor 1) circuit

S A/F sensor (bank 1, 2 sensor 1)

DI84D–01