Ford F150 Pickup. Instruction — part 1626

Fig. 22: Identifying Intake Air Temperature Sensors
Courtesy of FORD MOTOR CO.

Voltage that is dropped across a fixed resistor in a series with sensor resistor determines voltage signal at PCM.
This voltage signal is equal to reference voltage minus voltage drop across fixed resistor. IAT provides air
temperature information to PCM. PCM uses air temperature information as a correction factor in calculation of
fuel, spark and MAF. IAT sensor provides a quicker temperature change response time than ECT or CHT
sensor.

Supercharged vehicles use 2 IAT sensors. Both sensors are thermistors. However, one is located before the
supercharger at air cleaner for standard OBD-II cold weather input, while the second sensor (IAT2) is located
after the supercharger in intake manifold. IAT2 sensor located after supercharger provides air temperature
information to PCM to control border-line spark and to help determine intercooler (charge air cooler) efficiency.

Currently 2 types of IAT2 sensors are used on supercharged vehicles. A screw in type and an integrated type,
which is part of Thermal Manifold Absolute Pressure (TMAP) sensor. See Fig. 22 and Fig. 24 . TMAP sensor

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

consists of an IAT thermistor and a Manifold Absolute Pressure (MAP) sensor. The thermistor portion of
TMAP is used for IAT2 function and operates in the same manner as a non-integrated IAT2. For additional
information on the TMAP, see THERMAL MANIFOLD ABSOLUTE PRESSURE SENSOR .

Intake Manifold Runner Control

See VARIABLE INDUCTION SYSTEM under AIR INDUCTION SYSTEMS.

Intake Manifold Swirl Control

See VARIABLE INDUCTION SYSTEM under AIR INDUCTION SYSTEMS.

Intake Manifold Tuning Valve

See VARIABLE INDUCTION SYSTEM under AIR INDUCTION SYSTEMS.

Knock Sensor

The Knock Sensor (KS) is a tuned accelerometer located on the engine, which converts engine vibration to an
electrical signal. PCM uses this signal to determine the presence of engine knock and retards spark timing
accordingly.

Mass Airflow Sensor

Mass Airflow (MAF) sensor is located between air cleaner and throttle body, or inside air cleaner assembly.
MAF sensors use a hot wire sensing element to measure amount of air entering the engine. Air passing over the
hot wire causes it to cool. The hot wire is maintained at 392°F (200°C) greater than ambient temperature, as
measured by a constant cold wire. See Fig. 23 .

The current required to maintain hot wire operating temperature is proportional to the intake air mass flow.
MAF sensor outputs an analog voltage signal to PCM proportional to intake air mass. PCM uses this signal to
calculate fuel injector pulse width in order to provide the desired air/fuel ratio. On some applications, MAF
sensor input is used in determining transmission Electronic Pressure Control (EPC), shift and Torque Converter
Clutch (TCC) scheduling.

Most MAF sensors have Integrated By-Pass Technology (IBT) with an integrated Intake Air Temperature (IAT)
sensor.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

Fig. 23: Cross-Sectional View Of Mass Airflow Sensor (With IBT)
Courtesy of FORD MOTOR CO.

Output Shaft Speed Sensor

Output Shaft Speed (OSS) sensor provides PCM with information about rotational speed of transmission output
shaft. PCM uses information to control and diagnose powertrain behavior. In some applications, OSS sensor is
also used as source of monitoring vehicle speed. OSS sensor may be physically located in different places on
vehicle, depending upon the specific application. Design of each OSS sensor is unique and depends on which
powertrain control feature uses the information generated.

Power Steering Pressure Sensor

Power Steering Pressure (PSP) sensor monitors power steering pressure. PSP sensor voltage input to PCM will
change as hydraulic pressure changes. PCM uses PSP sensor input signal to compensate for additional loads on
engine by adjusting idle speed RPM, and prevents engine stall during parking maneuvers. PCM also uses PSP
signal to adjust transaxle/transmission Electronic Pressure Control (EPC) pressure during increased engine load.

Power Steering Pressure Switch

Power Steering Pressure (PSP) switch monitors power steering pressure. PSP switch is normally closed and

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

opens as pressure increases. PCM uses PSP switch input signal to compensate for additional loads on engine by
adjusting idle speed RPM, and prevents engine stall during parking maneuvers. PCM also uses PSP signal to
adjust transaxle/transmission Electronic Pressure Control (EPC) pressure during increased engine load.

Power Take-Off Switch

Power Take-Off (PTO) circuit is used by PCM to disable some OBD-II monitors during PTO operation. PTO
switch is normally open and circuit voltage is normally low. When PTO switch is closed, battery voltage is
supplied to PTO circuit, indicating an additional load condition to PCM. If an additional load condition is not
reported to PCM by PTO circuit, a false DTC may be stored.

Thermal Manifold Absolute Pressure Sensor

The Thermal Manifold Absolute Pressure (TMAP) sensor consists of a Manifold Absolute Pressure (MAP)
sensor and an integrated thermistor. The MAP portion of the sensor uses a piezo-resistive silicon sensing
element to provide a voltage proportional to the absolute pressure in the intake manifold. The thermistor portion
of the sensor operates in the same manner as an Intake Air Temperature (IAT) sensor. For additional
information on how the IAT sensor operates, see INTAKE AIR TEMPERATURE SENSOR .

For the Ranger 2.3L and Focus 2.3L PZEV, the TMAP sensor is part of the Exhaust Gas Recirculation (EGR)
system. The PCM uses information from the MAP portion of the TMAP sensor, Throttle Position (TP) sensor,
Mass Air Flow (MAF) sensor, Engine Coolant Temperature (ECT) sensor or Cylinder Head Temperature
(CHT) sensor and Crankshaft Position (CKP) sensor to determine how much exhaust gas is introduced into the
intake manifold. The thermistor portion of the TMAP sensor is currently not being used on this application.

For the Mustang 4.6L SC, the PCM uses manifold absolute pressure information from the MAP portion of the
TMAP sensor along with other sensor inputs to determine the proper amount of fuel needed for combustion
under varying engine load conditions. The thermistor portion of the TMAP sensor is used as a second IAT
sensor. This second IAT sensor, located after the supercharger, provides manifold air temperature information
to the PCM.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline