P2078

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

Wiring Diagram:

Circuit Description
The ECM applies a positive 5 volt reference voltage to the Intake Manifold Tuning (IMT) valve position sensor through the 5 volt reference circuit and the ground through the low reference circuit. The IMT valve position sensor provides signal voltage to the ECM that changes according the IMT valve position. The ECM monitors the IMT valve position sensor signal voltage. An IMT valve position sensor circuit DTC sets if the ECM detects the sensor signal voltage is outside the specified range.

Conditions for Setting the DTC
- Ignition ON with the engine running.
- IMT valve position sensor voltage is greater than 4.96 V for 2 seconds.

Action Taken When the DTCs Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn OFF at the end of 3 consecutive validation cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 warm up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.

Diagnostic Aids
If the DTC P2078 cannot be duplicated, the information included in the Freeze Frame data can be useful. Use the scan tool DTC information data to determine the status of the DTC.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. This step verifies that a condition exists.
4. This step tests the signal circuit for a short to voltage. If the scan tool displays a voltage after the TP sensor is disconnected, the circuit is shorted to a voltage.
6. This step tests for high resistance in the low reference circuit of the TP sensor. The ECM must be completely powered down to obtain an accurate resistance reading. It may take up to 30 minutes for the ECM to power down after the ignition key is removed. Removal of the ECM/TCM fuse allows the ECM to power down completely.
7. This step tests the low reference circuit for a short to voltage.

Step 1 - 2:

Step 3 - 13:

Step 14 - 17:

DTC Troubleshooting