Diagnostic Instructions

DTC Descriptors

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	P2077	P2077	P2077	P2078	--
IMT Valve Signal	P2077	P2077	P2077	P2078	--
Low Reference	--	P2078	P2078	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. The ECM can determine if the control circuit is open, shorted to ground, or shorted to voltage by monitoring the voltage on the IMT valve signal circuit.

Conditions for Running the DTC

Conditions for Setting the DTC

P2077

The ECM detects that the IMT valve position sensor is less than 0.04 volt for 2 seconds.

P2078

The ECM detects that the IMT valve position sensor is greater than 4.96 volts for 2 seconds.

Action Taken When the DTC Sets

DTCs P2077 and P2078 are Type A DTCs.

Conditions for Clearing the DTC

DTCs P2077 and P2078 are Type A DTCs.

Diagnostic Aids

If a shared 5-volt reference circuit is shorted to ground or shorted to a voltage, other 5-volt reference circuits may be affected.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Description and Operation:

Air Intake System Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. Verify DTCs P0642 or P0643 are not set.

⇒	If DTC P0642 or P0643 is set, refer to DTC P0642, P0643, P0698, or P0699 .

2. Engine idling, observe the scan tool DTC information parameter. DTCs P2077, and P2078 should not set.
3. If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the intake manifold tuning position sensor.
2. Ignition OFF for at least 20 seconds, test for less than 5 ohms of resistance between the low reference circuit and ground.

⇒	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 and ground.

⇒	If less than the specified range, test the 5-volt reference circuit for an open/high resistance or a short to ground. 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 voltage parameter is less than 0.3 volt.

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

5. Install a 3-A fused jumper wire between the signal circuit and the 5-volt reference circuit. Verify the scan tool IMT valve position sensor voltage parameter is greater than 4.8 volts.

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

Important: Perform the IMT Valve Relearn Procedure when replacing the IMT valve position sensor.

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.

Control Module References for engine control module replacement, setup, and programming