P0660

CIRCUIT DESCRIPTION
The intake air duct is divided into two separate runners connecting to the intake manifold tuning (IMT) valve plenum. The IMT valve plenum is an H type configuration containing the IMT valve assembly. During low speed, high load conditions the IMT valve is closed creating two separate runner paths in the incoming air ducts which aids an increasing torque. During higher engine speeds, above 3,200 RPM, the IMT valve opens creating a path between the two intake air duct runners allowing equalization of the intake air pressure which aids in increasing horsepower. The IMT valve is controlled by an IMT vacuum solenoid. Manifold vacuum is supplied to the IMT solenoid. A 12-volt supply from the manifold fuse to the IMT 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 vacuum to be applied to the IMT valve. When the IMT solenoid is commanded OFF, the voltage of the control circuit is high, battery voltage. When the IMT solenoid is commanded ON the voltage of the control circuit is low, near 0 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.

CONDITIONS FOR RUNNING THE DTC
- The engine speed is more than 40 RPM.
- The battery voltage is more than 8.05 volts and less than 18 volts.
- The ECM must change the state of the IMT solenoid from OPEN to CLOSED.

CONDITIONS FOR SETTING THE DTC
The voltage of the control circuit drops below a predetermined threshold.

ACTION TAKEN WHEN THE DTC SETS
- The control module stores the DTC information into memory when the diagnostic runs and fails.
- The malfunction indicator lamp (MIL) will not illuminate.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
- The driver information center, if equipped, may display a message.

CONDITIONS FOR CLEARING THE DTC
- A current DTC Last Test Failed clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
- Clear the DTC with a scan tool.

TEST DESCRIPTION

Steps 1-2:

Steps 3-9:

Steps 10-15:

The numbers below refer to the step numbers on the diagnostic table.
2. Listen for an audible click when the intake manifold tuning (IMT) solenoid operates. Command both the ON and OFF states. Repeat the commands as necessary.
4. Tests for voltage at the coil side of the IMT solenoid. The manifold fuse supplies power to the coil side of the IMT solenoid.
5. Verifies that the ECM is providing ground to the IMT solenoid.
6. Tests if ground is constantly being applied to the IMT solenoid.