Lexus ES300 (2002 year). Manual - part 399

051LT-07

05-30

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DIAGNOSTICS

SFI SYSTEM (1MZ-FE)

183

2002 LEXUS ES300 REPAIR MANUAL   (RM911U)

PROBLEM SYMPTOMS TABLE

Symptom

Suspect Area

See page

Engine does not crank (Does not start)

24.Starter

25.Starter relay

19-1
19-1

No initial combustion (Does not start)

1. ECM power source circuit

2. Fuel pump control circuit

3. ECM

05-178
05-173

01-31

No complete combustion (Does not start)

1. Fuel pump control circuit

05-173

Engine cranks normally (Difficult to start)

1. Starter signal circuit

2. Fuel pump control circuit

3. Compression

05-167
05-173

14-1

Cold engine (Difficult to start)

1. Starter signal circuit

2. Fuel pump control circuit

05-167
05-173

Hot engine (Difficult to start)

1. Starter signal circuit

2. Fuel pump control circuit

05-167
05-173

High engine idle speed (Poor idling)

1. A/C signal circuit (Compressor circuit)

2. ECM power source circuit

05-536
05-178

Low engine idle speed (Poor idling)

1. A/C signal circuit (Compressor circuit)

2. Fuel pump control circuit

05-536
05-173

Rough idling (Poor idling)

1. Compression

2. Fuel pump control circuit

3. Electric throttle control system

14-1

05-173

05-1 17

Hunting (Poor idling)

1. ECM power source circuit

2. Fuel pump control circuit

05-178
05-173

Hesitation/Poor acceleration (Poor driveability)

1. Fuel pump control circuit

2. A/T faulty

3. Electric throttle control system

05-173
05-384

05-133

Surging (Poor driveability)

1. Fuel pump control circuit

05-173

Soon after starting (Engine stall)

1. Fuel pump control circuit

05-173

During A/C operation (Engine stall)

1. A/C signal circuit (Compressor circuit)

2. ECM

05-536

01-31

Unable to refuel/Difficult to refuel

1. ORVR system

FI6929

A09074

A

B

B+

Power Transistor

Platinum Hot Wire 
(Heater)

Output
 Voltage

Temperature 
sensor

Platinum Hot Wire (Heater)

Temperature sensor

A53295

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DIAGNOSTICS

SFI SYSTEM (1MZ-FE)

05-31

184

2002 LEXUS ES300 REPAIR MANUAL   (RM911U)

DTC

P0100

MASS AIR FLOW CIRCUIT MALFUNCTION

CIRCUIT DESCRIPTION

The air flow meter uses a platinum hot wire. The hot wire air flow meter consists of a platinum hot wire, tem-
perature sensor and a control circuit installed in a plastic housing. The hot wire air flow meter works on the
principle that the hot wire and temperature sensor located in the intake air bypass of the housing detect any
changes in the intake air temperature.
The hot wire is maintained at the set temperature by controlling the current flow through the hot wire. This
current flow is then measured as the output voltage of the air flow meter.
The circuit is constructed so that the platinum hot wire and temperature sensor provide a bridge circuit, with
the power transistor controlled so that the potential of A and B remains equal to maintain the set temperature.

DTC No.

DTC Detecting Condition

Trouble Area

P0100

Open or short in air flow meter circuit with more than 3 sec.
engine speed less than 4,000 rpm

Open or short in air flow meter circuit

Intake air flow meter

ECM

If the ECM detects DTC 0100, it operates the fail-safe function, keeping the ignition timing and injection vol-
ume constantly and making it possible to drive the vehicle.
HINT:
After confirming DTC P0100, use the hand-held tester to confirm the mass air flow ratio from the CURRENT
DATA.

Air Flow Value (g/s)

Malfunction

Approx. 0.0

Air flow meter power source circuit open

VG circuit open or short

160.0 or more

EVG circuit open

051LU-07

A59741

B - G

Battery

FL MAIN

Engine Room J/B

B - W

E.F.I. ECU Relay

Intake Air 
Flow Meter

MREL

B - G

1

1

W - B

B - W

E2G

VG

5

3

2

1

6

1K

3

3

1

1B

R

2

2

5

1A

1C

ED

L - W

24

E9

32

E9

8

E6

ECM

E.F.I.

Engine
Room R/B

05-32

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DIAGNOSTICS

SFI SYSTEM (1MZ-FE)

185

2002 LEXUS ES300 REPAIR MANUAL   (RM911U)

WIRING DIAGRAM

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

READ VALUE OF OBD II SCAN TOOL OR HAND-HELD TESTER(MAF)

(a)

Read air flow rate on the hand-held tester.
Result:

A

B

Air flow rate (g/s)

0.0

160.0 or more

B

Go to step 5

A

A54396

+B

E2

A53763

E2

VG

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DIAGNOSTICS

SFI SYSTEM (1MZ-FE)

05-33

186

2002 LEXUS ES300 REPAIR MANUAL   (RM911U)

2

INSPECT INTAKE AIR FLOW METER SUB-ASSY

(a)

Disconnect the intake air flow meter connector.

(b)

Turn the ignition switch ON.

(c)

Measure voltage between the terminals +B and E2 of the
air flow meter harness side connector.
Voltage: 9 - 14 V

NG

Go to step 7

OK

3

INSPECT ECM

(a)

Start the engine.

(b)

Measure voltage between the terminals VG and E2 of the
ECM connector while the engine is idling.
Voltage: 0.5 - 3.0 V

HINT:
The shift position should be P or N and A/C switch should be
turned OFF.

OK

CHECK AND REPLACE ECM

NG