The engine control module (ECM) monitors the intake manifold pressure (IMP) sensor and controls the boost air system (mainly controlled by the VGT) and the engine turbocharger compressor bypass valve. The ECM also uses parameters like engine speed (RPM) and turbocharger speed to make a calculation of the IMP. This estimated value should not differ too much from the measured value.

Conditions for diagnostic trouble code (DTC):
1) Charge pressure High

Probable cause
1) Faulty VGT position – The sensor shows a more open position than the actual position
2) Faulty EGR position – Valve more closed than it is supposed to
3) Turbocharger
4) Charge air pressure sensor