Diagnostic Instructions

DTC Descriptor

DTC P0660: Intake Manifold Tuning (IMT) Valve Solenoid Control Circuit

DTC P2070: Intake Manifold Tuning (IMT) Valve Stuck Open

DTC P2071: Intake Manifold Tuning (IMT) Valve Stuck Closed

DTC P2076: Intake Manifold Tuning (IMT) Valve Position Sensor Performance

DTC P2077: Intake Manifold Tuning (IMT) Valve Position Sensor Circuit Low Voltage

DTC P2078: Intake Manifold Tuning (IMT) Valve Position Sensor Circuit High Voltage

Diagnostic Fault Information

Circuit	Short to Ground	High Resistance	Open	Short to Voltage	Signal Performance
IMT Valve Ignition Voltage	P0660, P2078	P2077	P0660, P2070, P2078	--	--
IMT Valve Ground	--	P2078	P2078	--	--
IMT Valve Control	P0660, P2071	P0660	P0660	None	--
IMT Valve Signal	P2077	P2070	P2078	P2070, P2078	P2070, P2071, P2076

Typical Scan Tool Data

IMT Valve Position

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: Ignition ON engine OFF. Normal range is open.
IMT Valve Ignition Voltage	Open	Open	Open
IMT Valve Ground	Open	Open	--
IMT Valve Control	Closed	Open	Open
IMT Valve Signal	Open	Open	Open

IMT Valve Feedback

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: Ignition ON engine OFF. Normal range is 18.4-25.2%.
IMT Valve Ignition Voltage	0%	0%	No Effect 18.4-25.2%
IMT Valve Ground	No Effect 18.4-25.2%	0%	--
IMT Valve Control	78-80%	18.4-25.2%	18.4-25.2%
IMT Valve Signal	100%	0%	0%

Circuit/System Description

An intake manifold tuning (IMT) valve 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. The IMT valve assembly consists of the following:

Ignition Voltage Circuit

An ignition voltage is supplied directly to the IMT valve assembly from the powertrain relay through a 10A fuse. The ignition voltage provides power to a microprocessor and to a motor that rotates the IMT valve within the intake manifold.

Ground Circuit

Ground circuit is supplied directly to the IMT valve assembly. This circuit provides ground for the micro-processor and the motor.

IMT Valve Control Circuit

During operation when the valve is open, the control module applies ground to the IMT valve control circuit which indicates to the microprocessor within the IMT valve to position the valve to the closed position which turns the motor ON and rotates the IMT valve within the intake manifold plenum.

IMT Valve Signal Circuit

When the IMT valve is rotated the hall-effect sensor is reporting the position of the valve to the engine control module (ECM). The control module uses this feedback signal to determine the position of the IMT valve.

The control module compares the commanded state of the IMT valve control circuit to the IMT valve signal circuit for being stuck open, stuck closed.

Conditions for Running the DTC

P2070, P2071, and P2076 only

Conditions for Setting the DTC

P0660

The ECM detects that the commanded state and the actual state of the IMT valve control circuit do not match. The ECM will detect an open, short to ground or short to voltage on the IMT valve control. It will also set a DTC if the IMT valve ignition voltage circuit is open, or short to ground. Each condition for more than 6.25 seconds.

P2070

The ECM detects that the IMT valve is stuck open. This diagnostic runs continuous when the conditions for running are met.

P2071

The ECM detects that the IMT valve is stuck closed. This diagnostic runs continuous when the conditions for running are met.

P2076

The ECM detects a difference between the actual IMT position and the desired IMT position.

P2077

The ECM detects a continuous short to ground or an open in either the IMT valve signal circuit or the IMT valve. This diagnostic runs continuous when the conditions for running are met.

P2078

The ECM detects an open in the IMT valve ground or a continuous short to voltage in either the IMT valve signal circuit or the sensor. This diagnostic runs continuous when the conditions for running are met.

Action Taken When the DTC Sets

DTCs P0660, P2070, P2071, P2076, P2077, P2078 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0660, P2070, P2071, P2076, P2077, P2078 are Type B DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Description and Operation

Intake Manifold Tuning Valve System Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Circuit/System Verification

1. Ignition ON engine OFF.
2. Command the IMT valve ON and OFF. The IMT valve Command parameter should transition from open to closed, and the IMT valve Feedback parameter should transition from 18.4-25.2 percent to 76.3-83.2 percent.

Circuit/System Testing

1. Ignition OFF, disconnect the IMT valve harness connector at the IMT valve.
2. Test for less than 1 ohm of resistance between the IMT valve ground circuit and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the IMT valve ignition 1 voltage circuit and ground.

⇒	If the test lamp does not illuminate, test the IMT valve ignition 1 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the fuse for the IMT valve ignition 1 voltage circuit is open, test or replace the IMT valve.

4. Connect a test lamp between the IMT valve control circuit and the IMT valve ignition 1 voltage circuit.
5. Command the IMT valve ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the IMT valve control circuit for a short to ground. If the circuit tests normal, replace the ECM.

⇒	If the test lamp is always OFF, test the IMT valve control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

6. Ignition ON, test for 4-6 volts between the IMT valve signal circuit and ground.

⇒	If less than the specified range, test the IMT valve signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

⇒	If greater than the specified range, test the IMT valve signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

7. Install a 3A fused jumper wire between the IMT valve signal circuit and ground. Verify the scan tool IMT valve Feedback parameter transitions from 0-100 percent.

⇒	If parameter does not change, test the IMT valve signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

8. If all circuits test normal, test or replace the IMT valve.

Component Testing

Important: If at any time the IMT valve blade becomes separated from the actuator, DO NOT cycle the actuator. Cycling the actuator without the blade attached will offset the calibration, and the entire IMT valve assembly will need to be replaced.

1. Remove the IMT valve.
2. Connect the IMT valve harness connector.
3. Turn ON the ignition and command the IMT valve ON and OFF using a scan tool. The IMT valve should rotate quickly from one position to another.

Repair Instructions

Important: If at any time the IMT valve blade becomes separated from the actuator, DO NOT cycle the actuator. Cycling the actuator without the blade attached will offset the calibration, and the entire IMT valve assembly will need to be replaced.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.