P0068
DTC P0068
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* ReviewStrategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptor
DTC P0068
- Throttle Body Airflow Performance
Circuit/System Description
The powertrain control module (PCM) uses the following information to calculate an expected airflow rate:
* The throttle position (TP)
* The barometric pressure (BARO)
* The manifold absolute pressure (MAP)
* The intake air temperature (IAT)
* The engine RPM
* The mass air flow (MAF)
Conditions for Running the DTC
* The engine is running.
* DTCs P0101, P0102, P0103, P0107, P0108, P1106, P1107, P1516, P1518, P2101, P2107, P2108, P2119, U0107 are not set.
* The DTC runs continuously when the above conditions are met.
Conditions for Setting the DTC
The PCM detects that the airflow rate is more than the calculated airflow for more than 0.2 second.
Action Taken When the DTC Sets
* DTC P0068 is a Type A DTC.
* The control module commands the TAC system to operate in the Reduced Engine Power mode.
Conditions for Clearing the MIL/DTC
DTC P0068 is a Type A DTC.
Reference Information
Schematic Reference
Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Throttle Actuator Control (TAC) System Description (Throttle Actuator Control (TAC) System Description)
Electrical Information Reference
* Wiring Repairs (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Circuit Testing (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Testing
1. Inspect for the following conditions:
* Vacuum hoses for splits, kinks, and proper connections as shown on Vehicle Emission Control Information label
* Inspect thoroughly for any type of leak or restriction
* Air leaks at throttle body mounting area and intake manifold sealing surfaces
* Inspect the throttle body for dirt, debris, and coking-Refer to Throttle Body Cleaning (Procedures).
2. Allow the engine to reach operating temperature. Observe the MAP Sensor Voltage parameter with a scan tool. The voltage should be more than 0.8 volt and less than 4 volts.
• If more than 4 volts or less than 0.8 volt, Refer to DTC P0106 (P0106).
3. Idle the engine. Observe the MAP Sensor kPa parameter with a scan tool. Increase the engine speed slowly and then back to idle. The MAP sensor kPa should change smoothly and gradually as engine speed is increased and returned to idle.
• If the MAP sensor kPa does not change, Refer to DTC P0106 (P0106).
4. Take a snapshot of the engine data list while performing the actions listed below. The MAF sensor g/s should change smoothly and gradually as the engine speed is increased and is returned to idle.
* Idle the engine.
* Increase the engine speed slowly to 3,000 RPM, then back to idle.
* Exit from the snapshot and review the data.
* Observe the Mass Air Flow (MAF) Sensor parameter frame by frame with a scan tool. The MAF sensor g/s should change smoothly and gradually as the engine speed is increased and is returned to idle.
• If the MAF sensor g/s does not change smoothly and gradually as the engine speed is increased and is returned to idle, Refer to DTC P0101 (P0101).
5. Inspect the throttle body for the following conditions:
* Loose or damaged throttle blade
* Broken throttle shaft
* Any throttle body damage
• If any of these conditions exist, replace the throttle body assembly.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Air Cleaner Element Replacement (Service and Repair)
* Lower Intake Manifold Replacement (Service and Repair)
* Manifold Absolute Pressure Sensor Replacement (Service and Repair)
* Mass Airflow Sensor/Intake Air Temperature Sensor Replacement (Service and Repair)
* Throttle Body Assembly Replacement (Removal and Replacement)
* Upper Intake Manifold Replacement (Service and Repair)