DTC P0068. Buick Allure 2009

For 1990-2009 cars only

Makes 🢒 Buick 🢒 2009 🢒 Allure 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P0068

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 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

Electrical Information Reference

•	Wiring Repairs

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Circuit Testing

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

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.

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.

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.

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.

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 after completing the diagnostic procedure.

•	Air Cleaner Element Replacement

•	Lower Intake Manifold Replacement

•	Manifold Absolute Pressure Sensor Replacement

•	Mass Airflow Sensor/Intake Air Temperature Sensor Replacement

•	Throttle Body Assembly Replacement

•	Upper Intake Manifold Replacement