1 MAP sensor
2 IAT sensor
NOTE: Not all versions are equipped with a MAP sensor. In these versions, the boost pressure is calculated from the engine speed, intake air mass and BARO parameters. These versions are equipped with a fixed geometry turbocharger with a pneumatic bypass valve (waste gate).
The MAP sensor is located in the air intake tract downstream of the intercooler. The MAP sensor has the following functions:
โข Measuring the current boost pressure,
โข Calculating the air density for adapting the injected quantity and the injection timing,
โข Calculating the turbocharger outlet temperature.
Effects of faults
In the event of a fault, the guide vanes of the variable geometry turbocharger are closed completely. Boost pressure is minimized.
Furthermore, the EGR system is deactivated and the injected fuel quantity is appreciably reduced (reduced engine power output).
Diagnosis
Within the framework of EOBD, the proper functioning of the MAP sensor is of great importance. Malfunctions lead to significantly increased emissions, as the EGR system is switched off and the boost pressure reduced to a minimum. For this reason, it is a MIL active component.
Monitoring of the MAP sensor consists of altogether three checking routines:
โข The range check determines whether the sensor values are within the limits. If the limits are not achieved or are exceeded for a certain period, the PCM interprets this as an open control loop or a short circuit.
โข The rise/fall check identifies intermittent faults. This indicates a loose contact at the sensor connector, among other things.
โข The plausibility check compares the MAP sensor signal with the BARO sensor signal.
The range check is activated when the ignition is switched on, provided that the PCM does not have a power supply fault. If the MAP sensor voltage exceeds the maximum limit, the PCM interprets this as a short to positive. If the MAP sensor voltage is below the minimum limit, the PCM interprets this as an open control loop or a short to ground.
The rise/fall check is also activated after the ignition is switched on, provided there is no fault in the power supply voltage to the sensor.
If the PCM identifies extreme, illogical voltage jumps below/above the limits, a relevant DTC is stored. The plausibility check takes place when the ignition is switched on (engine off). The plausibility check is only performed if the limit check was completed without any faults.
A prerequisite for this check, however, is that there is no plausibility fault entry stored in the fault memory of the PCM.
The PCM compares the current pressure at the MAP sensor with the pressure measured at the BARO sensor for a determined period. If the PCM detects an excessive deviation from the target map data, the PCM concludes that the MAP sensor is defective.
Typical malfunction limits:
โข Sensor voltage 4.8 V, corresponds to approx. 2.5 bar
โข Difference between MAP sensor und BARO sensor > 0.2 bar.
Possible diagnostic trouble codes: P0235, P0236, P0237.