1998 TOYOTA LAND CRUISER sensor

FI6929A09074A09707
Power Transistor
Output
Voltage
AB B+
Temperature Sensor
Platinum Hot Wire
Temperature Sensor
Platinum Hot Wire
- DIAGNOSTICSENGINE
DI-57
250 Author
: Date
:
2004 LAND CRUISER (RM1071U)
DTC P0100 Mass or Volume Air Flow Circuit
DTC P0102 Mass or Volume Air Flow Circuit Low Input
DTC P0103 Mass or Volume Air Flow Circuit High Input
CIRCUIT DESCRIPTION
The Mass Air Flow (MAF) meter measures the amount of air flowing through the throttle valve. The ECM uses
this information to determine the fuel injection time and provide a proper air fuel ratio. Inside the MAF meter,
there is a heated platinum wire exposed to the flow of intake air.
By applying a specific current to the wire, the ECM heats this wire to a given temperature. The flow of incom-
ing air cools the wire and an internal thermistor, affecting their resistance. To maintain a constant current
value, the ECM varies the voltage applied to these components in the MAF meter. The voltage level is pro-
portional to the airflow through the sensor. The ECM interprets this voltage as the intake air amount.
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 Detection ConditionTrouble Area
P0100Open or short in mass air flow meter circuit for more than 3
sec.
P0102Open or short in mass air flow meter circuit for more than 3
sec.
Open or short in mass air flow meter circuit

Mass air flow meter
P0103
Open in mass air flow meter circuit for more than 3 sec. (EVG
circuit)
Short in mass air flow meter circuit for more than 3 sec. (+B
circuit)
Mass air flow meter

ECM
DIC23-01

DI-58
- DIAGNOSTICSENGINE
251 Author
: Date
:
2004 LAND CRUISER (RM1071U)
HINT:
After confirming DTC P0100, P0102 or P0103, use the hand-held tester or the OBD II scan tool to confirm
the MAF ratio from the ALL menu (to reach the ALL menu: DIAGNOSIS / ENHANCED OBD II / DATA LIST
/ ALL).
Mass Air Flow Value (gm/sec.)Malfunction
Approx. 0.0
Mass air flow meter power source circuit open

VG circuit open or short
271.0 or more
EVG circuit open
MONITOR DESCRIPTION
If there is a defect in the MAF (Mass Air Flow) meter or an open or short circuit, the voltage level will deviate
outside the normal operating range. The ECM interprets this deviation as a defect in the MAF meter and sets
a DTC.
Example:
When the MAF meter voltage output is less than 0.2 V, or more than 4.9 V, and if either the condition contin-
ues for more than 3 sec.
MONITOR STRATEGY
P0100Mass air flow meter circuit range check
(Fluttering)
Related DTCsP0102Mass air flow meter circuit range check
(Low voltage)
P0103Mass air flow meter circuit range check
(High voltage)
Required sensors/componentsMass air flow meter
Frequency of operationContinuous
Duration3 sec.
MIL operationImmediate (When engine speed is at less than 4,000 rpm)
2 driving cycles (When engine speed is at 4,000 rpm or more)
Sequence of operationNone
TYPICAL ENABLING CONDITIONS
The monitor will run whenever the follow-
ing DTCs are not presentSee ºList of disable a monitorº (on page DI-3)
The typical enabling condition is not avail-
able-
TYPICAL MALFUNCTION THRESHOLDS
Detection CriteriaThreshold
P0100:
Mass air flow meter voltageLess than 0.2 V or more than 4.9 V
P0102:
Mass air flow meter voltageLess than 0.2 V
P0103:
Mass air flow meter voltageMore than 4.9 V

- DIAGNOSTICSENGINE
DI-65
258 Author
: Date
:
2004 LAND CRUISER (RM1071U)
DTC P0101 Mass or Volume Air Flow Circuit Range/
Performance Problem
CIRCUIT DESCRIPTION
Refer to DTC P0100, P0102 and P0103 on page DI-57.
DTC No.DTC Detecting ConditionTrouble Area
P0101
After engine is warmed up, conditions (a), (b), (c) and (d) con-
tinue for more than 10 seconds:
(2 trip detection logic)
(a) Throttle valve fully closed
(b) Voltage output of the mass air flow meter is more than 2.2
V.
(c) Engine coolant temperature is more than 70 °C (158 °F).
(d) Engine speed is less than 900 rpm.

Mass air flow meter
Conditions (a), (b) and (c) continue for more than 6 seconds
with engine speed: (2 trip detection logic)
(a) Engine speed is more than 0 rpm.
(b) VTA is more than 0.1 V.
(c) Voltage output of the mass air flow meter is less than 0.25
V.
MONITOR DESCRIPTION
The MAF (Mass Air Flow) meter helps the ECM calculate the amount of air flowing through the throttle valve.
The ECM uses this information to determine the fuel injection time and provide a proper air fuel ratio. Inside
the MAF meter, there is a heated platinum wire exposed to the flow of intake air. By applying a specific current
to the wire, the ECM heats this wire to a given temperature. The flow of incoming air cools the wire and an
internal thermistor, affecting their resistance. To maintain a constant current value, the ECM varies the volt-
age applied to these components in the MAF meter. The voltage level is proportional to the air flow through
the MAF meter. The ECM interprets this voltage as the intake air amount. If there is a defect in the MAF meter
or an open or short circuit, the voltage level will deviate outside the normal operating range. The ECM inter-
prets this deviation as a defect in the MAF meter and sets a DTC.
Example:
If the voltage is more than 2.2 V at idle or less than 0.25 V at idle OFF, the ECM interprets this as a defect
in the MAF meter and sets a DTC.
MONITOR STRATEGY
Related DTCsP0101Mass air flow meter rationality
Main sensors/componentsMass air flow meter
Required sensors/componentsRelated sensors/componentsEngine speed sensor, Engine coolant tempera-
ture sensor, Throttle position sensor
Frequency of operationContinuous
Duration10 sec. (High voltage)
6 sec. (Low voltage)
MIL operation2 driving cycles
Sequence of operationNone
DI1LC-17

- 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
A21047
Acceptable (Fig.1)
Resistance KW
Temp. C (F)
DI-68
- DIAGNOSTICSENGINE
261 Author
: Date
:
2004 LAND CRUISER (RM1071U)
DTC P0110 Intake Air Temperature Circuit
DTC P0112 Intake Air Temperature Circuit Low Input
DTC P0113 Intake Air Temperature Circuit High Input
CIRCUIT DESCRIPTION
The intake air temperature (IAT) sensor, mounted on the mass
air flow (MAF) meter, monitors the intake air temperature. The
IAT sensor has a thermistor that varies its resistance depending
on the temperature of the intake air. When the air temperature
is low, the resistance in the thermistor increases. When the tem-
perature is high, the resistance drops. The variations in resis-
tance are reflected as voltage changes to the ECM terminal.
(See Fig. 1).
The intake air temperature sensor is connected to the ECM
(See below ). The 5 V power source voltage in the ECM is ap-
plied to the intake air temperature sensor from terminal THA
(THAR) via 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 voltage at terminal THA (THAR) also
changes. Based on this signal, the ECM increases the fuel in-
jection volume to improve the driveability during cold engine op-
eration.
DTC No.Proceed toDTC Detection ConditionTrouble Area
P0110Step 1
Open or short in intake air
temperature sensor circuit for
0.5 sec.

Open or short in intake air temperature sensor circuit
P0112Step 4Short in intake air tempera-
ture sensor circuit for 0.5 sec.

Open or short in intake air temperature sensor circuit

Intake air temperature sensor (built in mass air flow meter)

ECM
P0113Step 2Open in intake air tempera-
ture sensor circuit for 0.5 sec.
ECM
HINT:
After confirming DTC ºP0110, P0112 or P0113º, use the hand-held tester or the OBD II scan tool to confirm
the intake air temperature in the ºDIAGNOSIS / ENHANCED OBD II / DATA LIST / ALLº.
Temperature DisplayedMalfunction
-40°C (-40°F)Open circuit
140°C (284°F) or moreShort circuit
DI1LE-13

- DIAGNOSTICSENGINE
DI-69
262 Author
: Date
:
2004 LAND CRUISER (RM1071U)
MONITOR DESCRIPTION
The ECM monitors the sensor voltage and uses this value to calculate the intake air temperature. When the
sensor output voltage deviates from the normal operating range, the ECM interprets this as a fault in the IAT
(Intake Air Temperature) sensor and sets a DTC.
Example:
When the sensor voltage output equal to -40C (-40F), or more than 140C (284F).
MONITOR STRATEGY
P0110Intake air temperature sensor range check
(Fluttering)
Related DTCsP0112Intake air temperature sensor range check
(Low resistance)
P0113Intake air temperature sensor range check
(High resistance)
Required sensors/componentsIntake air temperature sensor
Frequency of operationContinuous
Duration0.5 sec.
MIL operationImmediate
Sequence of operationNone
TYPICAL ENABLING CONDITIONS
The monitor will run whenever the follow-
ing DTCs are not presentSee ºList of disable a monitorº (on page DI-3)
The typical enabling condition is not avail-
able-
TYPICAL MALFUNCTION THRESHOLDS
Detection CriteriaThreshold
P0110:
Intake air temperature sensor resistance
(Intake air temperature)Less than 98.5 W, or more than 156 kW
(More than 140C (284F), or less than -40C (-40F)
P0112:
Intake air temperature sensor resistance
(Intake air temperature)Less than 98.5 W
(More than 140C (284F))
P0113:
Intake air temperature sensor resistance
(Intake air temperature)More than 156 kW
(Less than -40C (-40F))
COMPONENT OPERATING RANGE
ParameterStandard Value
Intake air temperature sensor resistance98.5 W (140C (284F)) to 156 kW (-40C (-40F))

A19549
THA
E2ECM
2
1
Mass Air
Flow Meter Mass Air
Flow Meter
12
M1
THA E2
M1
DI-72
- DIAGNOSTICSENGINE
265 Author
: Date
:
2004 LAND CRUISER (RM1071U)
2 Check for open in harness or ECM.
PREPARATION:
(a) Disconnect the M1 mass air flow meter connector.
(b) Connect terminals 1 and 2 of the mass air flow meter wire
harness side connector.
(c) Turn the ignition switch ON.
(d) When using hand-held tester, enter the following menus:
DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL / IN-
TAKE AIR.
CHECK:
Read the temperature value on the OBD II scan tool or the
hand-held tester.
OK:
Temperature value: 1405C (2845F) or more
OK Confirm good connection at sensor. If OK, re-
place mass air flow meter.
NG

- DIAGNOSTICSENGINE
DI-75
268 Author
: Date
:
2004 LAND CRUISER (RM1071U)
DTC P0115 Engine Coolant Temperature Circuit
DTC P0117 Engine Coolant Temperature Circuit Low
Input
DTC P0118 Engine Coolant Temperature Circuit High
Input
CIRCUIT DESCRIPTION
A thermistor is built in the Engine Coolant Temperature (ECT) sensor and changes the resistance value ac-
cording to the engine coolant temperature.
The structure of the sensor and connection to the ECM is the same the Intake Air Temperature (IAT) sensor.
HINT:
If the ECM detects the DTC ºP0115, P0117 or P0118º, it operates the fail-safe function in which the ECT
is assumed to be 80 C (176 F).
DTC No.Proceed toDTC Detection ConditionTrouble Area
P0115Step 1
Open or short in engine cool-
ant temperature sensor circuit
for 0.5 sec.
P0117Step 4
Short in engine coolant tem-
perature sensor circuit for 0.5
sec.
Open or short in engine coolant temperature sensor circuit

Engine coolant temperature sensor

ECM
P0118Step 2
Open in engine coolant tem-
perature sensor circuit for 0.5
sec.
HINT:
After confirming DTC ºP0115, P0117 or P0118,º use the OBD II scan tool or the hand-held tester to confirm
the engine coolant temperature from the DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL.
Temperature DisplayedMalfunction
-40°C (-40°F)Open circuit
140°C (284°F) or moreShort circuit
MONITOR DESCRIPTION
The ECT (Engine Coolant Temperature) sensor is used to monitor the engine coolant temperature. The ECT
sensor has a thermistor that varies its resistance depending on the temperature of the engine coolant. When
the coolant temperature is low, the resistance in the thermistor increases. When the temperature is high, the
resistance drops. The variations in resistance are reflected in the voltage output from the sensor.
The ECM monitors the sensor voltage and uses this value to calculate the engine coolant temperature.
When the sensor output voltage deviates from the normal operating range, the ECM interprets this as a fault
in the ECT sensor and sets a DTC.
Example:
When the ECM calculates that the ECT is less than -40C (-40F), or more than 140C (284F), and if either
the condition continues for 0.5 sec. or more, the ECM will set a DTC.
DI1LF-13

DI-76
- DIAGNOSTICSENGINE
269 Author
: Date
:
2004 LAND CRUISER (RM1071U)
MONITOR STRATEGY
P0115Engine coolant temperature sensor range check
(Fluttering)
Related DTCsP0117Engine coolant temperature sensor range check
(Low resistance)
P0118Engine coolant temperature sensor range check
(High resistance)
Required sensors/componentsEngine coolant temperature sensor
Frequency of operationContinuous
Duration0.5 sec.
MIL operationImmediate
Sequence of operationNone
TYPICAL ENABLING CONDITIONS
The monitor will run whenever the follow-
ing DTCs are not presentSee ºList of disable a monitorº (on page DI-3)
The typical enabling condition is not avail-
able-
TYPICAL MALFUNCTION THRESHOLDS
Detection CriteriaThreshold
P0115:
Engine coolant temperature sensor resistance
(Coolant temperature)Less than 79 W or more than 156 kW
(More than 140C (284F) or less than -40C (-40F))
P0117:
Engine coolant temperature sensor resistance
(Coolant temperature)Less than 79 W
(More than 140C (284F))
P0118:
Engine coolant temperature sensor resistance
(Coolant temperature)More than 156 kW
(Less than -40C (-40F))
COMPONENT OPERATING RANGE
ParameterStandard Value
Engine coolant temperature sensor resistance79 W (140C (284F)) to 156 kW (-40C (-40F))