Diagnose
Status September 2003 (EvoBus-Service / AFT)
Page: 63 of 83
4.1.19
Boost pressure
The boost pressure signal is read out and standardised in the 1 ms time slice. The calculated pressure is
then filtered every 10 ms time synchronised. The characteristic curve of the boost pressure sensor is
stored in the engine data record. If the voltage of the boost pressure sensor is above 4.90 V or below
0.24 V for more than 2 seconds, then the event "Measuring range exceeded or dropped below" is
detected and the fault code 1415 or 1416 is set. If these faults occur, the EGM switches into the Engine
protection: boost-pressure substitute value formation and calculates a substitute value for the boost
pressure.
In addition, the plausibility of the boost pressure sensor in the "Engine stopped" engine state is checked
with the signal of the atmospheric pressure sensor. With the engine at a standstill, the boost pressure
and atmospheric pressure must be approximately equal. If the pressure difference of both sensors is
greater than 100 mbar for at least 5 seconds, then the event "Measured value implausible" is detected
and the fault code 1417 is entered. The test only takes place when both the boost pressure and the
atmospheric pressure sensor show no fault electrically and the engine is stopped. In the case of an
implausible boost pressure, the engine remains largely available. The monitoring of the lambda correction
factor is cancelled and the engine continues to be operated with lambda control.
Characteristic curve: Boost pressure sensor
SEN - P charge air: sensor code
Charge air pressure [bar] = f(Sensor voltage [V])
Cha
rg
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ir pressure
Voltage