For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provide an overview of each diagnostic category.

### Circuit/System Description

An intake manifold tuning (IMT) valve or variable geometry induction system (VGIS) 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 IMT valve improves engine performance at low and high engine speeds depending on the engine load. Ignition 1 voltage is supplied directly to the IMT valve solenoid. The engine control module (ECM) controls the solenoid by grounding the control circuit. The IMT system contains the following components:

• | The IMT valve solenoid

• | The IMT valve vacuum reservoir

• | The IMT valve vacuum actuator

• | The intake manifold tuning valve

• | The intake manifold

### Reference Information

#### Description and Operation

Air Intake System Description

#### Special Tools Required

J 23738-A Vacuum Pump

### Circuit/System Verification

1. Engine idling, verify DTCs P0660, P0661, or P0662 are not set.

⇒ | If the DTC is set, refer to DTC P0660, P0661, or P0662 .

2. Engine idling, command the IMT valve ON with a scan tool. The IMT valve vacuum actuator should move to the closed position.

### Circuit/System Testing

1. Ignition OFF, disconnect the vacuum hose at the IMT valve vacuum actuator.
2. Connect a J 23738-A to the port of the vacuum actuator. Apply 51 kPa (15 inches H2O) of vacuum to the vacuum actuator. Verify the vacuum actuator moves, and that the vacuum remains steady.

⇒ | If the vacuum actuator does not move, replace the vacuum actuator.

⇒ | If the vacuum decreases, replace the vacuum actuator.

3. Connect the J 23738-A to the vacuum supply hose of the IMT valve vacuum actuator.
4. Engine idling, test for greater than 28 mm Hg (15 inches H2O).

⇒ | If less than the specified value, test for the following conditions:

• | A leak in the vacuum hoses, lines, or vacuum storage tank.

• | A blockage or restriction in hoses, lines, or vacuum storage tank.

• | A blockage or restriction at the intake manifold vacuum port

⇒ | If no condition is found, replace the IMT valve solenoid.

5. Engine idling, disconnect the IMT solenoid electrical connector. Verify that the vacuum remains steady for 30 seconds.

⇒ | If the vacuum decreases, replace the IMT valve solenoid.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Intake Manifold Tuning Valve Actuator Solenoid Replacement

• | Intake Manifold Tuning Valve Actuator Replacement

• | Intake Manifold Tuning Valve Vacuum Reservoir Replacement