Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Turbo Control Valve, By-Pass
When the throttle is closed high pressure is created between the turbo and the throttle because the turbocharger rotor and turbine need to time to slow down.
Turbo control valve bypass (also called the dump valve) opens when the pressure becomes too great. The pressure is reduced by the air being released back before the turbo. In this way the pressure can easily build up again, at the same time as the turbocharger rotor and turbine can maintain their speeds.
Too high a pressure between the turbo and a closed throttle would lead to too great a load and wear to the turbocharger when the air tries to penetrate backwards through the turbo.
By controlling the turbo control valve electrically, with a control signal (ground), the Engine Control Module (ECM) can select when the valve should open, that is select when the present boost pressure should be reduced.
The valve is supplied with voltage (12 V) from the engine compartment relay/fuse box.
The valve is diagnosed by the Engine Control Module (ECM) and the requested position can be read off.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.