Intake manifold tuning valve is used to increase torque at lower rpm and increase horsepower at higher rpm. Delta 2.7ℓ engine has two intake runners for each cylinder. The primary intake runner is a long, thin tube in which the intake air passes through. This allows a strong stream of air to blast into the cylinder, helping low-end torque. The secondary intake runner is a short, fat tube. This allows a large volume of air to be sucked into the engine, increasing high-end horsepower. At lower rpm range, the engine does not provide enough suction into the cylinders, starving the engine of much needed oxygen. The skinny tube helps blast the air into the cylinder for more oxygen. At higher rpm, the engine has plenty of suction but the intake runner is too small to provide the oxygen it needs. The short, fat tube allows plenty of oxygen to be sucked in. The ECM controls this function utilizing a intake manifold tuning valve. Based on engine RPM, the position of the shutter within the intake manifold is changed, thereby directing intake air through a longer path for low rpm range or a shorter path for high rpm range.

ECM sets DTC P0661 if the ECM detects that intake manifold tuning valve control circuit is shorted to ground.