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Home >> Buick >> 2015 >> Verano Leather >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 8 (Engine Controls And Fuel - 2.0L (LHU) - DTC P0010 To P0246) >> Diagnostic Information and Procedures >> DTC P0234 or P0299: Engine Underboost/Engine Overboost >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
  1. Verify the integrity of the entire air induction and exhaust system including all turbocharger components by inspecting for the conditions listed below:
    • The air intake duct system for loose clamps, cracks or other damage
    • The air intake duct system for being collapsed or restricted
    • Restricted air filter
    • An air flow restriction
    • Any type of air leak between the turbocharger and the throttle body, including the charge air cooler assembly
    • Splits, kinks or improper connections at the vacuum hoses
    • Any vacuum leak
    • Restricted, leaking or incorrect routing of vacuum or pressure hoses going to the components listed below:
      • Q42 turbocharger wastegate solenoid valve
      • Q40 turbocharger bypass solenoid valve
      • Intake manifold and turbocharger bypass valve vacuum tank
      • Turbocharger
      • Turbocharger wastegate actuator
      • Turbocharger bypass valve
    • Missing, restricted or leaking exhaust components. Refer to Symptoms - Engine Exhaust .
    • Exhaust leak between the turbocharger and the exhaust manifold
    • Restricted or leaking turbocharger oil supply line
    • Loose or incorrect installation of any components
      • If a condition exists, repair as necessary.
  2. Ignition OFF, disconnect the vacuum supply hose from the Q40 turbocharger bypass solenoid valve and connect the J-23738-A  mityvac or a suitable vacuum gauge to the hose.
    3. NOTE:
    • Engine temperature, accessory load, and elevation level will affect engine vacuum.
    • Vacuum readings will decrease by approximately 2.7 kPa (0.8 in Hg) for every 305 m (1, 000 ft) of elevation above sea level.
  3. Engine Idling, the gauge should read between 47-68 kPa (14-20 in Hg).
    • If not within the specified range, inspect and repair the vacuum source or the vacuum leak in the areas listed below:
    • The vacuum hose between the Q40 turbocharger bypass solenoid valve and the turbocharger bypass valve vacuum tank
    • The turbocharger bypass valve vacuum tank
    • The vacuum hose between the turbocharger bypass valve vacuum tank and the intake manifold
  4. Ignition OFF, disconnect the J-23738-A  mityvac or vacuum gauge and reconnect the hose to the Q40 turbocharger bypass solenoid valve
  5. Disconnect the vacuum hose from the turbocharger bypass valve and connect the J-23738-A  mityvac or a suitable vacuum gauge to the hose.
  6. Engine Idling, command the turbocharger bypass solenoid valve between Active and Inactive with a scan tool while observing the vacuum gauge. The gauge should read between 47-68 kPa (14-20 in Hg) when commanded Active and 0 kPa (0 in Hg) when commanded Inactive.
    • If not within the specified range, inspect the vacuum hose for a leak or restriction. If a condition is found, replace the hose. If a condition is not found, replace the Q40 turbocharger bypass solenoid valve.
  7. Ignition OFF, inspect the turbocharger bypass valve assembly for damage. Refer to Turbocharger Cleaning and Inspection (LDK, LHU) .
    • If a condition is found, replace the turbocharger bypass valve as necessary.
  8. Disconnect the hose from the turbocharger wastegate actuator.
  9. Connect the J-23738-A  mityvac to the actuator and apply 51 kPa (15 inches Hg) of vacuum. The actuator should hold vacuum for at least 10 s
    • If vacuum is not held for at least 10 s, replace the turbocharger
  10. Using the exhaust/pressure port on the J-23738-A  mityvac, or a suitable hand pressure pump, apply between 0-80 kPa (0-12 psi) pressure to the wastegate actuator. The wastegate actuator rod should move throughout the range.
    • If the wastegate actuator rod does not move throughout the range, replace the turbocharger.
  11. Disconnect the turbocharger wastegate solenoid valve supply hose at the turbocharger and connect the J-23738-A  mityvac to the hose.
  12. Apply 51 kPa (15 inches Hg) of vacuum to the Q42 turbocharger wastegate solenoid valve. Verify the pressure decreases to 0 kPa (0 inches Hg) when commanding the Turbocharger Wastegate Solenoid Valve to 25 % with a scan tool.
    • If not the specified value, replace the Q42 turbocharger wastegate solenoid valve.
  13. Inspect the turbocharger assembly for damage or foreign material. Refer to Turbocharger Cleaning and Inspection (LDK, LHU) .
    • If a condition is found, repair or replace the turbocharger assembly as necessary.
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