Bosch-Common Rail System – MAP sensor

The illustration shows the MAP sensor in a vehicle with a diesel particulate filter system

The MAP sensor is located in the air intake tract downstream of the intercooler. The MAP sensor has the following functions:
• Measuring the current boost pressure,
• Calculating the air density for adapting the injected quantity and the injection timing,
• Calculating the turbocharger outlet temperature.

Effects of faults

In the event of a fault, the guide vanes of the variable geometry turbocharger are opened completely. Boost pressure is minimized. Furthermore, the EGR system is deactivated and the injected fuel quantity is appreciably reduced (reduced engine power output).

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.

The monitoring system continuously checks whether the values output by the MAP sensor are within limits. Furthermore, a plausibility check is performed in the monitoring system. It is however only performed if the limit check was completed without any faults.

The plausibility check takes place at a set low engine speed. Here, the PCM compares the current pressure at the MAP sensor with the pressure measured at the BARO sensor for a defined period of time.

If the system detects an excessive deviation from the target map data, it concludes immediately that the MAP sensor is defective and changes over to a substitute parameter.

Possible diagnostic trouble codes: P0235, P0236, P0237, P0238.

07. August 2018 by Ron
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