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MAF Sensor

Mass Airflow (MAF) Sensor

MONITOR DESCRIPTION

The MAF sensor monitors the amount of air flowing through the throttle valve. The engine control module
(ECM) uses this information to determine the fuel injection time and provide a proper air/fuel ratio. Inside
the MAF sensor, 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, changing their resistance. To maintain a constant current value, the ECM varies the
voltage applied to these components in the MAF sensor. The voltage level is proportional to the airflow
through the sensor and the ECM interprets this voltage as the intake air amount. If there is a defect in the
sensor 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 sensor and sets a DTC.

MONITOR STRATEGY

Related DTCs P0

100 MAF sensor is open/shorted
R i d /C t
Main MAF sensor
Required sensors/Components
Sub Crankshaft position sensor
Frequency of operation Continuous
Duration Within 10 sec.
MIL ti
Immediate Engine RPM is less than 4,000 rpm
operation
2 driving cycles Engine RPM is 4,000 rpm or more
Sequence of operation None

TYPICAL ENABLING CONDITIONS

The monitor will run whenever the following DTCs are not present See page In

−4

TYPICAL MALFUNCTION THRESHOLDS

Detection Criteria Threshold
MAF lt
Less than 0.2 V
sensor voltage
More than 4.9 V

COMPONENT OPERATING RANGE

Parameter Standard Value
MAF sensor voltage Between 0.5 V and 4.5 V

Ce-2
Components - Engine Inputs

Information developed by Toyota. Used with permission.

Ce-2

Mass Airflow (MAF) Sensor Range/Performance Problem

MONITOR DESCRIPTION

The MAF sensor measures the amount of air flowing through the throttle valve. The engine control module
(ECM) uses this information to determine the fuel injection time and provide a proper air/fuel ratio. Inside
the MAF sensor, 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, changing their resistance. To maintain a constant current value, the ECM varies the
voltage applied to these components in the MAF sensor. The voltage level is proportional to the airflow
through the sensor and the ECM interprets this voltage as the intake air amount.
In order to confirm that the output voltage of MAF sensor corresponds to the actual intake air amount, the
ECM checks the output voltage of the MAF sensor under the following conditions:

S

During idle (small intake air volume)

S

While driving under a high load condition (large intake air volume)
If the ECM detects that the output voltage of the MAF sensor is high while the engine is idling or the output
voltage is low while driving under a high load condition, the ECM interprets this as a malfunction in the MAF
sensor and sets a DTC.

MONITOR STRATEGY

Related DTCs P0

101 MAF sensor malfunction
R i d /C t
Main MAF sensor
Required sensors/Components
Sub Crankshaft position sensor, Throttle position sensor and ECT sensor
Frequency of operation Continuous
Duration Within 10 sec.
MIL operation 2 driving cycles
Sequence of operation None

TYPICAL ENABLING CONDITIONS

The monitor will run whenever the following DTCs are not present See page In

−4
Included in the Typical Malfunction Thresholds −

TYPICAL MALFUNCTION THRESHOLDS

Detection Criteria Threshold Typical Enabling Condition
MAF lt
More than 2.2 V

S

Idling

S

ECT is 70°C (158°F) or more
sensor voltage
Less than 1.0 V

S

Engine RPM is 2000 rpm or more

S

Throttle valve open

COMPONENT OPERATING RANGE

Parameter Standard Value
MAF sensor voltage Between 0.5 V and 4.5 V

A20390

Volt (V)
mmHg
kPa

1

50
Intake Manifold Absolute Pressure
450 750 840
20 60 100 (112)
Output Voltage
(3.96)
3.6
2.4

1

.2

Sensor Specification

Components - Engine Inputs
Ce-3

Information developed by Toyota. Used with permission.

Ce-3

MAP Sensor

Manifold Air Pressure (MAP) Sensor

MONITOR DESCRIPTION

The MAP sensor detects the air pressure in the intake manifold.
The ECM uses this sensor to calculate the engine load. Engine
load is one of the factors the ECM uses to determine the fuel
injector ON time, i.e. the fuel injection quantity. The sensor always
indicates a “pressure” in the intake manifold as a complete
vacuum is interpreted as “zero” pressure. Manifold pressures
vary from a low values during idle or deceleration
conditions to “atmospheric” pressure at wide

−open throttle.

Supercharged
or turbocharged engines will achieve pressure
above atmospheric pressure.
The ECM supplies a regulated 5 V reference−voltage to the
MAP sensor. The MAP sensor varies its outputs signal voltage
between 1.2 V and 3.96 V in response to the pressure variations
in the intake manifold. When the pressure in the intake
manifold is low, the output voltage of the MAP sensor is low.
When the pressure is high, the output voltage is high.
If the ECM detects a MAP sensor output voltage that is out of
the specified range, the ECM interprets this as a malfunction in
the MAP sensor and sets a DTC.

MONITOR STRATEGY

Related DTCs P0

105 MAP sensor circuit is open/shorted
R i d /C t
Main MAP sensor
Required sensors/Components
Sub None
Frequency of operation Continuous
Duration Within 10 sec.
MIL operation Immediate
Sequence of operation None

TYPICAL ENABLING CONDITIONS

The monitor will run whenever the following DTCs are not present See page In

−4

TYPICAL MALFUNCTION THRESHOLDS

Detection Criteria Threshold
MAP sensor voltage Less than 0.5 V or more than 4.5 V

COMPONENT OPERATING RANGE

Parameter Standard Value
MAP sensor voltage Between

1.2 V (at −80 kPa) and 3.96 V (at 12 kPa)

A20390

Volt (V)
mmHg
kPa

1

50
Intake Manifold Absolute Pressure
450 750 840
20 60 100 (112)
Output Voltage
(3.96)
3.6
2.4

1

.2

Sensor Specification

Ce-4
Components - Engine Inputs

Information developed by Toyota. Used with permission.

Ce-4

Manifold Air Pressure (MAP) Sensor Range/Performance Problem

MONITOR DESCRIPTION

TheMAP sensor detects the air pressure (vacuum) in the intake
manifold. The ECM uses this sensor to calculate the engine
load. Engine load is one of the factors the ECM uses to determine
the fuel injector ON time, i.e. the fuel injection quantity.
The sensor always indicates a “pressure” in the intake manifold
as a complete vacuum is interpreted as “zero” pressure. Manifold
pressures vary from a low value during idle or a deceleration
condition to higher value at wide

−open throttle (atmospheric
pressure level). Supercharged or turbocharged engines will
achieve pressure above atmospheric pressures.
The ECM supplies a regulated 5V reference−voltage to the
MAP sensor. The MAP sensor varies its outputs signal voltage
between 1.2 V and 3.96 V in response to the pressure variations
in the intake manifold. When the pressure in the intake
manifold is low, the output voltage of the MAP sensor is low.
When the pressure is high, the output voltage is high.
To confirm that the output voltage of the MAP sensor corresponds
to the actual pressure in the intake manifold, the ECM
checks the MAP sensor output voltage in the following conditions:

S

While idling (low intake manifold pressure)

S

While the engine is in a high−load condition (high intake
manifold pressure)
If the ECM detects a high output voltage from the MAP sensor
while the engine is idling or a low output voltage when the engine
is highly loaded, the ECM interprets this as a malfunction
in the MAP sensor and sets a DTC.

MONITOR STRATEGY

Related DTCs P0

106 MAP sensor malfunction
R i d /C t
Main MAP sensor
Required sensors/Components
Sub Crankshaft position sensor, Throttle position sensor and ECT sensor
Frequency of operation Continuous
Duration Within 10 sec.
MIL operation 2 driving cycles
Sequence of operation None

TYPICAL ENABLING CONDITIONS

The monitor will run whenever the following DTCs are not present See page In

−4
Included in the Typical Malfunction Thresholds −

Components - Engine Inputs
Ce-5

Information developed by Toyota. Used with permission.

CE-5

TYPICAL MALFUNCTION THRESHOLDS

Detection Criteria Threshold Typical Enabling Condition
MAP lt
More than 3.0 V

S

Idling

S

ECT is 70°C (158°F) or more
sensor voltage
Less than 1.0 V

S

Engine RPM is less than 2,500 rpm

S

Throttle valve open

COMPONENT OPERATING RANGE

Parameter Standard Value
MAP sensor voltage Between

1.2 V (at 20 kPa) and 3.96 V (at 112 kPa)

A

15475

Acceptable
Resistance k

Ω

−

20 0 20 40 60 80 100
(− 4) (32) (68) (104) (140) (176) (212)
30
20

1

0

1

0.

1

Temperature

°C (°F)

Sensor Specification

Ce-6
Components - Engine Inputs

Information developed by Toyota. Used with permission.

Ce-6

IAT Sensor

Intake Air Temperature (IAT) Sensor

MONITOR DESCRIPTION

The IAT sensor mounted on the mass airflow (MAF) sensor*,
monitors temperature of the intake air. 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 temperature is
high, the resistance drops. The variations in resistance are reflected
in the voltage output from the sensor. The ECMmonitors
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 malfunction in the IAT
sensor and sets a DTC.
* When the engine uses a manifold air pressure (MAP) sensor
instead of a MAF sensor, the IAT sensor is mounted on the air
cleaner box.

MONITOR STRATEGY

Related DTCs P0

110 IAT sensor circuit is open/shorted
R i d /C t
Main IAT sensor
Required sensors/Components
Sub None
Frequency of operation Continuous
Duration Within 10 sec.
MIL operation Immediate
Sequence of operation None

TYPICAL ENABLING CONDITIONS

The monitor will run whenever the following DTCs are not present See page In

−4

TYPICAL MALFUNCTION THRESHOLDS

Detection Criteria Threshold

IAT sensor circuit is shorted:

IAT sensor resistance (temperature of intake air) Less than 98.5

Ω (more than 140°C [284°F])

IAT sensor circuit is open:

IAT sensor resistance (temperature of intake air) More than 156 kΩ (less than −40°C [−40°F])