P2078
DTC P2077 or P2078
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P2077
- Intake Manifold Tuning Control Valve Position Sensor Circuit Low Voltage
DTC P2078
- Intake Manifold Tuning Control Valve Position Sensor Circuit High Voltage
Diagnostic Fault Information
Circuit/System Description
The intake manifold tuning valve controls the length of the intake runners in the intake manifold. The intake manifold contains both long and short runners. The tuning valve controls only the short runners. When the valve is closed, the short runners are blocked, which forces the air through the long runners. This results in tuning effects in the manifold that increases the torque produced by the engine at lower engine speeds. When the valve is open, both the long runners and short runners are open, but the majority of the air travels through the short runners, since the air will naturally follow the shortest path into the cylinder. This allows the air to flow through the short runners, which results in increased torque at higher engine speeds.
Ignition voltage is supplied directly to the intake manifold tuning valve actuator. The engine control module (ECM) controls the valve actuator motor by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage signal.
The tuning valve actuator contains a position sensor, which outputs a pulse width modulated (PWM) signal, to detect the actual position of the tuning valve in relation to its commanded position. Variations in the duty cycle of the PWM signal enables the ECM to detect a physically broken, restricted or stuck tuning valve.
Conditions for Running the DTC
* The ignition is ON or the engine is operating.
* The DTCs run continuously once the above condition is met for greater than 4 s.
Conditions for Setting the DTC
P2077
The ECM detects a continuous open or short to low in the intake manifold tuning valve position sensor circuit.
P2078
The ECM detects a continuous short to high in the intake manifold tuning valve position sensor circuit.
Action Taken When the DTC Sets
DTC P2077 and P2078 are Type B DTCs.
Conditions for Clearing the DTC
DTC P2077 and P2078 are Type B DTCs.
Diagnostic Aids
If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the scan tool circuit test status parameters for the component. A circuit test status parameter will change from OK or Not Run to Malfunction if there is a condition with the circuit or a connection.
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Air Intake System Description Air Intake System Description
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON
2. Verify that DTC P2077, or P2078 is not set.
• If any of the DTCs are set
Refer to Circuit/System Testing
• If none of the DTCs are set.
3. 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.
4. Verify a DTC does not set.
• If a DTC sets
Refer to Circuit/System Testing
• If a DTC does not set
5. All OK
Circuit/System Testing
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the Q22 Intake Manifold Tuning Solenoid Valve. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 5 ohms between the ground circuit terminal 2 and ground.
• If 5 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 2 ohms
3. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 1 and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF, remove the test lamp.
2. Test for less than 2 ohms in the ignition voltage circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF, remove the test lamp.
2. Test for infinite resistance between the ignition voltage circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
Note: The vehicle may not be equipped with each circuit and component as listed below.
3. Test for greater than 10 ohms between each of the ignition circuits listed below and ground:
* Ignition circuit terminal 1 - B52A Heated Oxygen Sensor 1
* Ignition circuit terminal 1 - B52B Heated Oxygen Sensor 2
* Ignition circuit terminal 2 - E41 Engine Coolant Thermostat Heater
* Ignition circuit terminal 2 - Q12 Evaporative Emission Purge Solenoid
• If 10 ohms or less, disconnect the appropriate component and retest to verify if the short is in the circuit or the component.
• If greater than 10 ohms, replace the intake manifold
• If the test lamp illuminates
4. Ignition ON, test for 4.8-5.2 V between the signal circuit terminal 4 and ground.
• If less than 4.8 V
1. Ignition OFF, disconnect the X2 harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the signal circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K20 Engine Control Module.
• If greater than 5.2 V
1. Ignition OFF, disconnect the X2 harness connector at the K20 Engine Control Module.
2. Ignition ON, test for less than 1 V between the signal circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K20 Engine Control Module.
• If between 4.8-5.2 V
5. Replace the Intake Manifold.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Intake Manifold Replacement
* Control Module References Control Module References for ECM replacement, programming, and setup.