1996 TOYOTA LAND CRUISER Workshop Manual

DI5OZ−02
A00152
Output Voltage
Power Transistor
B+
Thermistor
Platinum Hot Wire
A B
Thermistor Platinum Hot Wire
FI6929 P22263
DI−20
−
DIAGNOSTICS ENGINE
1996 LAND CRUISER (RM451U)
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 met\
er consists of a platinum hot wire,
thermistor and a control circuit installed in a plastic housing. The hot wire air f\
low meter works on the principle
that the hot wire and thermistor located in the intake air bypass of the hou\
sing detect any changes in the
intake air temperature.
The hot wire is maintained at the set temperature by controlling the curren\
t flow through the hot wire. This
current flow is then measured as the output voltage of the air flow mete\
r.
The circuit is constructed so that the platinum hot wire and thermistor pro\
vide a bridge circuit, with the power
transistor controlled so that the potential of ”A” and ”B” remains equ\
al to maintain the set temperature.
DTC No.DTC Detecting ConditionTrouble Area
P0100Open or short in mass air flow meter circuit with 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, k\
eeping the ignition timing and injection
volume constant and marking 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 ”CURRENT DATA”.
Mass Air Flow Value (gm/sec.)Malfunction
Approx. 0Mass air flow meter power source open
 VG circuit open or short
439.0 or moreE21 circuit open
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P22419
WR−Y
GECM
Y−R R
R
BR
Battery Fusible Link
EFI
R/B No.2
EFI Main
Relay
Y−R
FL MAIN
BR
1
Mass Air Flow
Meter
2
2 2
2 2
2
1 1
1
F8 2
4
3 E7
E5
E5 VGMRLY
2
23
7
5 16B+
E1
EB
E21
EB1 EA2
−
DIAGNOSTICS ENGINE
DI−21
1996 LAND CRUISER (RM451U)
WIRING DIAGRAM
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A00201
ON
BE6653
P24652
DI−22
−
DIAGNOSTICS ENGINE
1996 LAND CRUISER (RM451U)
INSPECTION PROCEDURE
1 Connect the OBD II scan tool or TOYOTA hand −held tester, and read value of
mass air flow rate.
PREPARATION:
(a) Remove the fuse cover on the instrument panel.
(b) Connect the OBD II scan tool or TOYOTA hand−held tester to the DLC3.
(c) Turn ignition switch ON and OBD II scan tool or TOYOTA hand−held tester main switch ON.
(d) Start the engine.
CHECK:
Read 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.)Approx. 0 gm/sec.439.0 gm/sec. or more
Type I Go to step 2.
Type II Go to step 5.
2 Check voltage of mass air flow meter power source.
PREPARATION:
(a) Disconnect the mass air flow meter connector.
(b) Turn ignition switch ON.
CHECK:
Measure voltage between terminal 1 of mass air flow meter con-
nector and body ground.
OK:
Voltage: 9 − 14 V
NG Check for open in harness and connector between EFI main relay (Marking: EFI) and
mass air flow meter (See page IN−28 ).
OK
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P24653
VG
(+)
(−)
−
DIAGNOSTICS ENGINE
DI−23
1996 LAND CRUISER (RM451U)
3 Check voltage between terminal VG of ECM and body ground.
PREPARATION:
(a) Remove instrument panel speaker No.1 panel
(See page SF−65).
(b) Start the engine.
CHECK:
Measure voltage between terminal VG of ECM and body
ground while 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−28 ).
NG
4 Check for open and short in harness and connector between mass air flow \
meter and ECM (See page IN−28 ).
NG Repair or replace harness or connector.
OK
Replace mass air flow meter.
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P24654
(+)
(−)E21
DI−24
−
DIAGNOSTICS ENGINE
1996 LAND CRUISER (RM451U)
5 Check continuity between terminal E21 of ECM and body ground.
PREPARATION:
Remove instrument panel speaker No.1 panel
(See pageSF−65).
CHECK:
Check continuity between terminal E21 of ECM and body
ground.
OK:
Continuity (1 Ω or less)
NG Check and replace ECM (See page IN−28 ).
OK
6 Check for open in harness and connector between mass air flow meter and \
ECM (See page IN−28 ).
NG Repair or replace harness or connector.
OK
Replace mass air flow meter.
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−
DIAGNOSTICS ENGINE
DI−25
1996 LAND CRUISER (RM451U)
DTC P0101 Mass Air Flow Circuit Range/Performance
Problem
CIRCUIT DESCRIPTION
Refer to DTC P0100 (Mass Air Flow Circuit Malfunction) on page DI−20.
DTC No.DTC Detecting ConditionTrouble Area
P0101
Conditions (a) and (b) continue with engine speed 900 rpm or
less (2 trip detection logic):
(a) Closed throttle position switch: ON
(b) Mass air flow meter output > 2.2 V
Mass air flow meterConditions (a) and (b) continue with engine speed 1500 rpm
(2 trip detection logic):
(a) Mass air flow meter output < 1 V
(b) VTA  0.72 V
WIRING DIAGRAM
Refer to DTC P0100 (Mass Air Flow Circuit Malfunction) on page DI−20 for the WIRING DIAGRAM.
INSPECTION PROCEDURE
1 Are there any other codes (besides DTC P0101) being output?
YES Go to relevant DTC chart.
NO
Replace mass air flow meter.
DI5P0−02
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FI4741
(fig.1)Acceptable
Resistance kΩ
− 20 0 20 40 60 80 100
( − 4) 32 68 104 140 176 212
30
20
10
53
2
1
0.5
0.3
0.2
0.1
Temp. °C (F °)
DI−26
−
DIAGNOSTICS ENGINE
1996 LAND CRUISER (RM451U)
DTC P0110 Intake Air Temp. Circuit Malfunction
CIRCUIT DESCRIPTION
The intake air temperature sensor is built into the air flow meter
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
(See next page). The 5 V power source voltage in the ECM is
applied to the intake air temperature sensor from the terminal
THA via a resistor R.
That is, the 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).
Intake Air Temp.
° C (° F)Resistance
(kΩ)Voltage
(V)
−20 (− 4)16.24.3
0 (32)5.93.4
20 (68)2.52.4
40 (104)1.11.4
60 (140)0.60.9
80 (176)0.30.5
100 (212)0.10.2
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
 ECM
HINT:
After confirming DTC P110 use the OBD II scan tool or TOYOTA hand −held tester to confirm the intake air
temp. from ”CURRENT DATA”.
Temp. DisplayedMalfunction
− 40° C (− 40°F)Open circuit
140°C (284°F) or moreShort circuit
DI5P1−02
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A00484
Intake Air Temp. Sensor
(Inside the mass air flow meter)
3
4 L−Y
BR−B 5V
ECM
E5
E5
THA
E1
E2
P22420
3
9 R
−
DIAGNOSTICS ENGINE
DI−27
1996 LAND CRUISER (RM451U)
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:
If DTCs P0110 (Intake Air Temp. Circuit Malfunction), P0115 (Engine Coolant Temp. Circuit Malfunction),
P0120 (Throttle/Pedal Position Sensor/Switch ”A” Circuit Malfunction)\
are output simultaneously, E2 (Sen-
sor Ground) may be open.
1 Connect the OBD II scan tool or TOYOTA hand −held tester, and read value of
intake air temperature.
PREPARATION:
(a) Remove the fuse cover on the instrument panel.
(b) Connect the OBD II scan tool or TOYOTA hand−held tester to DLC3.
(c) Turn ignition switch ON and OBD II scan tool or TOYOTA hand−held tester main switch ON.
CHECK:
Read temp. value on the OBD II scan tool or TOYOTA hand −held tester.
OK:
Same as actual intake air temp.
HINT:
If there is open circuit, push OBD II scan tool or TOYOTA hand− held tester indicates − 40° C (− 40°F).
If there is short circuit, OBD II scan tool or TOYOTA handheld tester indicates 140° C (284°F) or more.
NG − 40° C (− 40 °F) ....Go to step 2.
140 °C (284°F) or more ....Go to step 4.
OK
Check for intermittent problems
(See page DI−3 ).
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