Diagnostic Instructions

DTC Descriptors

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
5-Volt Reference	P0107, P0405, P0452, P0651, P2077, P2106, P2106	P2076	P2077	P0651, P2076	--
IMT Valve Signal	P2077	P2076	P2077	P2078	P2076
Low Reference	--	P2076	P2078	--	--

Circuit/System Description

The engine control module (ECM) supplies the intake manifold tuning (IMT) valve position sensor with a 5-volt reference circuit, a low reference circuit, and a signal circuit. The IMT valve position sensor provides a signal voltage that changes relative to the IMT valve angle.

Conditions for Running the DTC

P2076

P2077 or P2078

Conditions for Setting the DTC

P2076

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

P2077

The ECM detects that the IMT valve position sensor is less than 0.3 volt for 5 seconds.

P2078

The ECM detects that the IMT valve position sensor is greater than 4.8 volts for 5 seconds.

Action Taken When the DTC Sets

Conditions for Clearing the DTC

Diagnostic Aids

Reference Information

Schematic Reference

Engine Controls Schematics

Description and Operation

Air Intake System Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. Verify DTC P0651 is not set.

⇒	If DTC P0651 is set, refer to DTC P0641 or P0651.

2. Engine running, command the IMT valve ON with a scan tool and observe the IMT valve vacuum actuator moves to the closed position.

⇒	If the IMT valve vacuum actuator is inoperative, refer to Intake Manifold Tuning Valve Diagnosis for further diagnosis.

3. Engine running, observe the DTC information with a scan tool. DTCs P0660, P2076, P2077, and P2078 should not set.

⇒	If DTC P0660 is set, refer to DTC P0660 for further diagnosis.

4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the IMT valve position sensor.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 3 and ground.

Important:  If the circuit is shorted to a voltage, the low reference circuit within the ECM may open and the ECM will also need to be replaced.

⇒	If greater than the specified range, test the low reference circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the ECM.

Important: The 5-volt reference circuits are internally and externally connected at the ECM. Other component DTCs may be set. If other DTCs are set, review the electrical schematic and diagnose the applicable circuits and components.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 1 and ground.

⇒	If less than the specified range, test the 5-volt reference 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 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Verify the scan tool IMT valve position sensor percentage parameter is less than 5 percent.

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

5. Install a 3A fused jumper wire between the signal circuit terminal 2 and the 5-volt reference circuit terminal 1. Verify the scan tool IMT valve position sensor percentage parameter is greater than 95 percent.

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

6. If all circuits test normal, test or replace the IMT valve position sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.