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Control valve, bypass

Control valve, bypass


During deceleration, there is a build up of pressure at the turbocharger outlet at the same time as the flow rapidly drops. This will result in the turbocharger pumping (cavitating), which means that a powerful pulsation arises in the compressor inlet and outlet. This cavitation can result in compressor damage and noise as well as the mass air flow sensor measuring an incorrectly large air mass, as the air moves backwards and forwards through the intake system during cavitation.

A bypass valve is fitted between the compressor outlet and inlet to prevent the compressor from pumping. The valve is opened by vacuum from the intake manifold.



In a de-energized state, a solenoid valve will connect the bypass valve control line to the intake manifold after the throttle. During deceleration, the vacuum will open the bypass valve and connect the turbocharger outlet and inlet, preventing cavitation. During acceleration, the solenoid valve will operate and the control line will be connected before the throttle. This ensures that the bypass valve is closed securely under normal driving conditions.

The solenoid valve is powered from the main relay and is grounded from control module pin 51.





Diagnostics


• If there is an open circuit or short circuit to ground, diagnostic trouble code P1658 will be generated.

• If there is a short circuit to B+, diagnostic trouble code P1659 will be generated.

• In the event of an internal leak in the bypass valve, the current air mass/combustion will not reach the requested air mass/combustion.