2001 TOYOTA AVALON Service Repair Manual

A00307
ON
VSV is ON VSV is OFF
Air Filter Air
Air
E
FE
F
BE6653
FI7073 FI7074
DI-146
- DIAGNOSTICSENGINE
302 Author
: Date
:
2001 AVALON (RM808U)
INSPECTION PROCEDURE
TOYOTA hand-held tester:
1 Connect TOYOTA hand-held tester, and check operation of VSV for ACIS.
PREPARATION:
(a) Remove the fuse cover on the instrument panel.
(b) Connect the TOYOTA hand-held tester to the DLC3.
(c) Turn the ignition switch ON and TOYOTA hand-held tes-
ter main switch ON.
(d) Select the INTAKE CTRL VSV from the ACTIVE TEST
menu on the TOYOTA hand-held tester.
CHECK:
Check the operation of the VSV when the VSV is operated by
the TOYOTA hand-held tester.
OK:
VSV is ON:
Air from port E flows out through port F.
VSV is OFF:
Air from port E flows out through the air filter.
OK Check vacuum tank (See page SF-46).
NG
2 Check VSV for ACIS (See page SF-68).
NG Replace VSV for ACIS.
OK
3 Check for open and short in harness and connector between EFI main relay
(Marking: EFI) and ECM (See page IN-30).
NG Repair or replace harness or connector.
OK

A11824
ON
ACIS
(+)
(-)ACI1
- DIAGNOSTICSENGINE
DI-147
303 Author
: Date
:
2001 AVALON (RM808U)
Check and replace ECM (See page IN-30).
OBD II scan tool (excluding TOYOTA hand-held tester):
1 Check VSV for ACIS (See page SF-68).
NG Replace VSV for ACIS.
OK
2 Check voltage between terminals ACIS, ACI1 of ECM connector and body
ground.
PREPARATION:
(a) Remove the glove compartment (See page SF-82).
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminals ACIS, ACI1 of the ECM
connector and body ground.
OK:
Voltage: 9 - 14 V
NG Check for open and short in harness and con-
nector between EFI main relay (Marking: EFI)
and ECM (See page IN-30).
OK
3 Check vacuum tank (See page SF-58).
NG Repair or replace.
OK
Check and replace ECM (See page IN-30).

DI07F-09
A06106
B+
Thermister
Power Transister
Platinum Hot Wire
B
Output
Voltage A
FI6929
S05741
- DIAGNOSTICSENGINE
DI-23
179 Author
: Date
:
2001 AVALON (RM808U)
CIRCUIT INSPECTION
DTC P0100 Mass Air Flow Circuit Malfunction
CIRCUIT DESCRIPTION
The mass air flow meter uses a platinum hot wire. The hot wire air flow meter consists of a platinum hot wire,
thermistor and a control circuit installed in a plastic housing. The hot wire air flow meter works on the principle
that the hot wire and thermistor 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 thermistor 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 ConditionTrouble Area
P0100Open or short in mass air flow meter circuit with more than 3
sec. engine speed 4,000 rpm or less
Open or short in mass air flow meter circuit

Mass air flow meter

ECM
If the ECM detects DTC P0100 it operates the fail-safe function, keeping the ignition timing and injection
volume constantly and making it possible to drive the vehicle.
HINT:
After confirming DTC P0100, use the OBD II scan tool or TOYOTA hand-held tester to confirm the mass
air flow ratio from the CURRENT DATA.
Mass Air Flow Value (gm/sec.)Malfunction
0.0
Mass air flow meter power source circuit open

VG circuit open or short
271.0 or more
E2G circuit open

A11668
Engine Room J/B
EFI No.1
2G
2B 2A
2F2
5
1 3
2B-W
4L-O
4 2
EFI No.2 EFI Relay
From BatteryB
Mass Air
Flow Meter3
2 1
EDW-B
R-BECM
E2GVG
E2 R10
19
E5E5
From
Terminal
MREL of
ECM
DI-24
- DIAGNOSTICSENGINE
180 Author
: Date
:
2001 AVALON (RM808U)
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:
Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool. Because freeze frame records
the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining
whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean
or rich, etc. at the time of the malfunction.
1 Connect OBD II scan tool or TOYOTA hand-held tester, and read value of mass
air flow rate.
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand-held tester to the DLC3.
(b) Turn the ignition switch ON and push the OBD II scan tool or TOYOTA hand-held tester main switch
ON.
(c) Start the engine.
CHECK:
Read the mass air flow rate on the OBD II scan tool or TOYOTA hand-held tester.
RESULT:
Type IType II
Mass Air Flow Rate (gm/sec.)0.0271.0 or more
Type I Go to step 2.
Type II Go to step 5.

A00436
ON
4
BE6653
S05337
(+)
(-)
A02017
VG
(+)
(-)
- DIAGNOSTICSENGINE
DI-25
181 Author
: Date
:
2001 AVALON (RM808U)
2 Check voltage of mass air flow meter power source.
PREPARATION:
(a) Disconnect the mass air flow meter connector.
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminal 4 of the mass air flow
meter connector and body ground.
OK:
Voltage: 9 - 14 V
NG Check for open in harness and connector be-
tween EFI main relay (Marking: EFI) and mass
air flow meter (See page IN-30).
OK
3 Check voltage between terminal VG of ECM connector and body ground.
PREPARATION:
(a) Remove the glove compartment (See page SF-82).
(b) Start the engine.
CHECK:
Measure the voltage between terminal VG of the ECM connec-
tor and body ground while the engine is idling.
OK:
Voltage:
1.1 - 1.5 V (P or N position and A/C switch OFF)
OK Check and replace ECM (See page IN-30).
NG
4 Check for open and short in harness and connector between mass air flow meter
and ECM (See page IN-30).
NG Repair or replace harness or connector.
OK

A02018
E2G
DI-26
- DIAGNOSTICSENGINE
182 Author
: Date
:
2001 AVALON (RM808U)
Replace mass air flow meter.
5 Check continuity between terminal E2G of ECM connector and body ground.
PREPARATION:
Remove the glove compartment (See page SF-82).
CHECK:
Check the continuity between terminal E2G of the ECM con-
nector and body ground.
OK:
Continuity (1 W or less)
NG Check and replace ECM (See page IN-30).
OK
6 Check for open in harness and connector between mass air flow meter and ECM
(See page IN-30).
NG Repair or replace harness or connector.
OK
Replace mass air flow meter.

- DIAGNOSTICSENGINE
DI-27
183 Author
: Date
:
2001 AVALON (RM808U)
DTC P0101 Mass Air Flow Circuit Range/Performance
Problem
CIRCUIT DESCRIPTION
Refer to DTC P0100 on page DI-23.
DTC No.DTC Detecting ConditionTrouble Area
P0101
Conditions (a), (b) and (c) continue 10 sec. or more with en-
gine speed NE < 900: (2 trip detection logic)
(a) Throttle valve fully closed
(b) Mass air flow meter output  2.2 V
(c) THW  70°C

Mass air flow meterP0101
Conditions (a) and (b) continue 10 sec. or more with engine
speed 1,500 rpm or more: (2 trip detection logic)
(a) VTA  0.63 V
(b) Mass air flow meter output
1.06 V

Mass air flow meter
INSPECTION PROCEDURE
HINT:
Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool. Because freeze frame records
the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining
whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean
or rich, etc. at the time of the malfunction.
1 Are there any other codes (besides DTC P0101) being output?
NO Replace mass air flow meter.
YES
Go to relevant DTC chart (See page DI-14).
DI07G-09

FI4741
Fig. 1
Acceptable
Resistance kW
- 20 0 20 40 60 80 100
(- 4) (32) (68) (104) (140) (176) (212) 30
20
10
5
3
2
1
0.5
0.3
0.2
0.1
Te m p .°C (F°)
DI-28
- DIAGNOSTICSENGINE
184 Author
: Date
:
2001 AVALON (RM808U)
DTC P0110 Intake Air Temp. Circuit Malfunction
CIRCUIT DESCRIPTION
The intake air temperature sensor is built into mass air flow me-
ter and senses the intake air temperature.
A thermistor built in the sensor changes the resistance value
according to the intake air temperature.
The lower the intake air temperature, the greater the thermistor
resistance value, and the higher the intake air temperature, the
lower the thermistor resistance value (See Fig. 1).
The intake air temperature sensor is connected to the ECM.
The 5 V power source voltage in the ECM is applied to the in-
take air temperature sensor from terminal THA via resistor R.
That is, resistor R and the intake air temperature sensor are
connected in series. When the resistance value of the intake air
temperature sensor changes in accordance with changes in the
intake air temperature, the potential at terminal THA also
changes. Based on this signal, the ECM increases the fuel in-
jection volume to improve driveability during cold engine opera-
tion.
If the ECM detects the DTC P0110, it operates the fail-safe
function in which the intake air temperature is assumed to be
20°C (68°F).
DTC No.DTC Detecting ConditionTrouble Area
P0110Open or short in intake air temp. sensor circuit

Open or short in intake air temp. sensor circuit

Intake air temp. sensor (built into mass air flow meter)

ECM
HINT:
After confirming DTC P0110, use the OBD II scan tool or TOYOTA hand-held tester to confirm the intake
air temperature form the CURRENT DATA.
Temperature DisplayedMalfunction
-40°C ( -40°F )Open circuit
140°C ( 284°F ) or moreShort circuit
DI07H-10