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.

### 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

• | DTC P0660 is not set.

• | The engine is operating for greater than 1 second.

• | The intake air temperature is greater than 15°C (59°F).

• | The manifold absolute pressure (MAP) is less than 30 kPa for 6 seconds.

• | The IMT valve is enabled for greater than 1 second.

• | The DTC runs continuously once the above conditions are met.

#### P2077 or P2078

• | DTC P0660 is not set.

• | The engine is operating for greater than 5 seconds.

• | The DTCs run continuously once the above condition is met.

### 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

• | DTC P2076 is a Type B DTC.

• | DTCs P2077 and P2078 are Type A DTCs.

### Conditions for Clearing the DTC

• | DTC P2076 is a Type B 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.

• | The scan tool 5 volt reference parameter should display between 4.8-5.2 volts.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls Connector End Views

#### Description and Operation

Air Intake System Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### 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 idling, 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 idling, 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. 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 List.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector of the IMT valve position sensor.
2. Ignition OFF, test for less than 5 ohms of resistance 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 5 ohms, test the low reference circuit for a short to voltage, or an open/high resistance. If the circuit/connections test 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 4.8 volts, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the ECM.

⇒ | If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.

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

⇒ | If greater than 5 percent, test the signal circuit for a short to voltage. If the circuit/connections test 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 95 percent, test the signal circuit for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the ECM.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Intake Manifold Tuning (IMT) Valve Position Sensor Replacement.

• | Control Module References for ECM replacement, setup, and programming