Circuit/System Description

The intake manifold tuning (IMT) valve system uses variable air induction tuning in order to achieve maximum performance and efficiency over the entire operating range of the engine. The characteristic torque curve of a normally aspirated engine depends mainly on how the engines average pressure changes over the engine speed range. The average pressure is proportional to the volume of the air mass present in the cylinder when the inlet valve is closed. The design of the inlet system determines how large an air mass can be drawn into a cylinder at a given engine speed. An IMT valve is used to change the intake manifold plenum configuration. When the IMT valve is open, the intake manifold is configured to one large plenum. When the IMT valve is closed, the intake manifold is configured to 2 smaller plenums. The 2 intake manifold plenum sizes result in different torque curves, which improves performance at low and high engine speeds. During low speed, high load conditions the IMT valve is closed, creating a longer runner path inside the plenum, which increases torque. During higher engine speeds and loads, the IMT valve opens creating a shorter runner path inside the plenum, which increases horsepower.

The IMT valve actuator solenoid has the following circuits:

• Ignition 1 voltage circuit
• IMT Valve Actuator Solenoid Control Circuit

An IMT valve position sensor is mounted on the intake manifold and attached to the shaft of the IMT valve. The IMT valve position sensor has the following circuits:

• A 5 volt reference circuit
• Low reference circuit
• Signal circuit

The purpose of this diagnostic is to verify the open/closed position of the IMT valve by using the voltage signal supplied by the sensor to the ECM when it is commanded ON and OFF.