GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2006 🢒 Optra 🢒 Restraints 🢒 SIR 🢒 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 engine control module (ECM) compares actual airflow based on throttle position (TP) and manifold absolute pressure (MAP) sensor to a calculated airflow.

Conditions for Running the DTC
    • The engine is running.
    • DTCs P0106, P0107, P0108, P0110, P0111, and P0112 are not set.
    • The DTC runs continuously when the above conditions are met.

Conditions for Setting the DTC

The ECM detects that the actual airflow rate is more than the calculated airflow.

Action Taken When the DTC Sets
    • DTC P0068 is a Type A DTC.
    • The ECM commands the TAC system to operate in a Reduced Engine Power mode.
    • The ECM commands the reduced engine power indicator ON.
    • DTCs P2106 and P2110 will set.

Conditions for Clearing the DTC

DTC P0068 is a Type A DTC.

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

Throttle Actuator Control (TAC) 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

    Important: In extreme cold weather conditions ice may form in the vacuum source to the MAP sensor and may set a DTC. Inspect the MAP sensor and the vacuum source for ice, moisture, or other restrictions.

  1. Ignition ON, observe the manifold absolute pressure (MAP) sensor pressure parameter and compare the reading on the scan tool to the barometric pressure table. Refer to Altitude Versus Barometric Pressure .
    2. ⇒If the MAP sensor pressure is not within the range specified for your altitude, refer to DTC P0107 or P0108 .
  2. Start the engine, observe the MAP Sensor parameter. The reading should be between 32-42 kPa.
  3. 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 Data List.

Circuit/System Testing
  1. Verify that none of the following conditions exist:
    2. • The air intake duct system for loose connecting clamps, cracks, or other damage
    • The air intake duct system for being collapsed or restricted possibly by a restricted air filter
    • A damaged throttle body blade or shaft
    • Splits, kinks, or improper connections at the vacuum hoses
    • Missing, restricted, or leaking exhaust components--Refer to Symptoms - Engine Exhaust .
    • Vacuum leaks at the intake manifold, throttle body, and injector O-rings
  2. If all conditions test normal, test the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical .

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Throttle Body Assembly Replacement
    •  Air Cleaner Assembly Replacement