Depending on the system, either a MAP sensor and an IAT sensor or a T-MAP sensor is installed. In the T-MAP sensor, the MAP sensor and the IAT sensor are combined to form a single component.
The boost pressure in the intake manifold is measured by means of the MAP sensor. The higher the boost pressure, then the greater the maximum quantity of fuel that can be injected as a function of accelerator pedal position or engine load.
The MAP signal influences the following functions:
โข Injected fuel quantity,
โข EGR system,
โข turbo control.
The IAT sensor measures the intake air/charge air temperature.
The signal serves as a correction factor to take into account the effect of temperature on the density of the charge air.
The IAT signal influences the following functions:
โข Injected fuel quantity,
โข Injection timing,
โข EGR system.
Possible consequences of faults (MAP)
A faulty MAP signal leads to restricted operation of the boost pressure control as well as the EGR system. The injection quantity must therefore be reduced (reduced engine power output).
Possible consequences of faults (IAT)
In the event of a signal failure, the PCM performs the calculations using a predetermined substitute value. This can lead to loss of power.
Diagnosis (MAP and IAT)
The monitoring system checks:
โข the sensor for short circuit to ground/battery and open control loop.
โข the sensor for illogical voltage jumps (illogical voltage jumps could indicate a loose connection, for example).
โข whether the output signal corresponds to the map data.