Intake Air Temperature/Intake Manifold Pressure Sensor

Intake Air Temperature/Intake Manifold Pressure Sensor

Intake air temperature/intake manifold pressure sensor
The intake air temperature and intake-manifold pressure sensor is bolted onto the intake plenum.
This combined sensor delivers the following information to the engine control system:
- Temperature after the throttle valve
- Intake pipe vacuum after the throttle valve
The intake-air temperature / intake-manifold pressure sensor is used to calculate the intake air flow rate. The pressure also serves as a substitute value for the load signal.

Functional description

Intake-manifold pressure sensor
Strain gauge are used for detecting the pressure. A steel membrane equipped with strain gauge in the sensor is deformed by the adjacent pressure. The changes in resistance in the strain gauge are electronically detected by a Wheatstone bridge and evaluated. The measured voltage is then included as an actual value in the charge-air-pressure control.

Intake air temperature sensor
A temperature-dependent electrical resistor is used for temperature sensing. The circuit contains a voltage divider where the resistance can be measured depending on the temperature. A temperature is converted using a characteristic curve specific to the sensor. An NTC resistor is installed in the intake air temperature sensor; its resistance value falls as the temperature rises. The resistance changes from 167 k ohms to 150 ohms depending on temperature, which corresponds to a temperature of -40 °C to 130 °C.







Structure and inner electrical connection
The intake air temperature/intake-manifold pressure sensor is connected by a 4-pin plug connection.
The sensor is supplied with 5 Volts by the engine control.







Characteristic curve and setpoint values
The information on the intake pipe vacuum is transmitted to the engine control via a signal line. The signal for evaluation of the intake pipe vacuum fluctuates depending on the pressure. The measuring range of approx. 0.5 to 4.5 volts corresponds to an air pipe vacuum of 15 kPa (0.15 bar) to 120 kPa (1.2 bar).







The resistance of the intake air temperature sensor is temperature-dependent and varies between 167 k ohms and 150 ohms. This corresponds to a temperature of -40°C to 130 °C.

Observe the following setpoint values for the intake-manifold pressure sensor:

Size Value
Voltage range of intake- 0.5 to 4.5 volts
manifold pressure sensor

Measuring range of air 0.15 to 1.2 bar
intake pressure

Intake air temperature ±1 °C
resolution

Maximum output current 10 mA

Temperature range -40 °C to 130 °C

Diagnosis instructions

Failure of the component

If the intake-air temperature / intake-manifold pressure sensor fails, the following behaviour is to be expected:
- Fault entry in the engine control unit
- Emergency operation with substitute value
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.