DTC P2008: Intake Manifold Runner Control - Control Circuit Low: Description

The intake manifold upper plenum is divided into two separate runners, one for each bank, by an Intake Manifold Runner Control (IMRC) valve. During low speed, high load conditions the IMRC valve is closed creating a longer runner path inside the plenum which increases torque. During higher engine speeds, above 3,200 RPM, the IMRC valve opens creating a shorter runner path inside the plenum which increases horsepower. The IMRC valve is controlled by an IMRC vacuum solenoid. Manifold vacuum is supplied to the IMRC solenoid. A 12-volt supply from the manifold fuse to the IMRC solenoid is applied when the ignition key is turned ON. The solenoid is normally closed which will not allow vacuum to pass through it. When the engine speed and load are increased above a calibrated threshold, the Engine Control Module (ECM) provides a ground to the solenoid, energizing the solenoid and allowing a vacuum to be applied to the IMRC valve. When the IMRC solenoid is commanded OFF, the voltage of the control circuit is high, battery voltage. When the IMRC solenoid is commanded ON, the voltage of the control circuit is low, near zero volts. The ECM applies a pull up voltage of 2.6-4.6 volts on the control circuit to differentiate between an open, a short to ground, or a short to voltage.