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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 145 (Engine Control System & Fuel - 4.8L, 5.3L, 6.0L And 6.2L - DTC P0335 To DTC P3449) >> DTC P0506 or P0507 >> Circuit/System Verification

Circuit/System Verification

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  1. If there are any other DTCs set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
  2. Compare the desired engine idle speed to the actual engine idle speed with a scan tool. Actual engine idle speed should be no greater than or less than 100 RPM of desired RPM.
  3. Command the engine speed up and down with a scan tool. Increase the engine speed in 25 RPM increments while comparing the desired engine speed to the actual engine speed. The actual engine speed should stay within 25 RPM of the desired engine speed.
  4. Inspect for any condition that can reduce idle speed by increasing engine load.
    • Incorrect torque converter clutch (TCC) operation
    • Accessories that require additional torque to operate
    • Excessive deposits in the throttle body-Refer to Throttle Body Cleaning .
    • Restricted exhaust-Refer to Restricted Exhaust .
    • Mechanical conditions that limit engine speed
  5. Inspect for any condition that can increase idle speed.
    • Vacuum leaks
    • Unmetered air entering the engine after the mass air flow
    • A faulty positive crankcase ventilation (PCV) valve
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