GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 Engine 🢒 Engine Controls - 2.5L (LBK) 🢒 Intake Manifold Tuning Valve Diagnosis

Circuit 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 two 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 valve 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

Test Description

The number below refer to the step number on the diagnostic table.

  1. This step determines that the IMT valve and linkage is moving correctly and not loose or damaged.

  1. This step test for a faulty IMT valve solenoid. If the IMT valve solenoid is commanded ON, there should be vacuum at the vacuum actuator. If the IMT valve solenoid is commanded OFF, there should be no vacuum at the vacuum actuator.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Important: This table diagnoses the mechanical portion of the intake manifold tuning (IMT) valve system.

  1. Turn ON the ignition, with the engine OFF.
  2. Observe the DTC information with a scan tool.

Is DTC P0661, or P0662 set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Inspect the IMT valve system for the following conditions:
    3. • Disconnected, restricted, or damaged vacuum hoses. Refer to Emission Hose Routing Diagram .
    • Disconnected or damaged components.
    • Binding vacuum actuator linkage.
    • Linkage that is interfering with hoses, wiring, or any other components.
    • Internally binding IMT valve. Refer to Intake Manifold Replacement in Engine mechanical 2.5L (LBK).

Did you find and correct the condition?

--

Go to Step 12

Go to Step 4

4
  1. Disconnect the vacuum supply hose at the vacuum actuator.
  2. Connect a J 23738-A Vacuum Pump to the supply hose of the vacuum actuator.
  3. Start and idle the engine.
  4. Observe the vacuum gage of the vacuum pump.

Is the vacuum on the gage more than the specified value?

33 kPa (10 Hg)

Go to Step 5

Go to Step 6

5

  1. Turn OFF the engine.
  2. Connect a J 23738-A Vacuum Pump to the vacuum actuator.
  3. Apply the specified amount of vacuum.
  4. Observe the vacuum gage of the vacuum pump.

Does the vacuum increase and is the vacuum holding?

33 kPa (10 Hg)

Go to Intermittent Conditions

Go to Step 10

6
  1. Connect the vacuum supply hose at the vacuum actuator.
  2. Disconnect the vacuum supply hose at the IMT valve solenoid.
  3. Connect the J 23738-A to the supply hose of the IMT valve solenoid.
  4. Observe the vacuum gage of the vacuum pump.

Is the vacuum on the gage more than the specified value?

33 kPa (10 Hg)

Go to Step 7

Go to Step 8

7

  1. Turn OFF the engine.
  2. Connect the vacuum supply hose at the IMT valve solenoid.
  3. Disconnect the outlet hose at the IMT valve solenoid.
  4. Connect a J 23738-A to the outlet port of the IMT valve solenoid.
  5. Start and idle the engine.
  6. With a scan tool, command the IMT valve solenoid ON and OFF.
  7. Observe the vacuum gage of the vacuum pump.

Is the vacuum on the gage more than the specified value?

33 kPa (10 Hg)

Go to Step 9

Go to Step 11

8

Repair one of the following conditions:

    • A restricted or leaking vacuum supply hose between the reservoir and the IMT valve solenoid.
    • A restricted or leaking vacuum supply hose between the intake manifold and the reservoir.
    • A restricted port on the intake manifold.
    • A vacuum reservoir port that is restricted or a vacuum reservoir that is leaking. Refer to Intake Manifold Tuning Valve Vacuum Reservoir Replacement

Did you complete the repair?

--

Go to Step 12

--

9

Repair the leaking or restricted vacuum hoses between the IMT valve solenoid and the vacuum actuator.

Did you complete the repair?

--

Go to Step 12

--

10

Replace the IMT valve vacuum actuator valve. Refer to Intake Manifold Tuning Valve Actuator Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the IMT valve solenoid. Refer to Intake Manifold Tuning Valve Actuator Solenoid Replacement .

Did you complete the replacement?

--

Go to Step 12

--

12
  1. Connect all disconnected components.
  2. Start the engine.
  3. Operate the system in order to verify the repair.

Did you correct the condition?

--

Go to Step 13

Go to Step 2

13

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK