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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 111 (Engine Controls Self-Diagnostics - 2.2L CNG) >> Diagnostic Tests >> DTC P0171: Fuel Trim System Lean >> Test Description

Test Description

WARNING: This page is about a different car, the 2002 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

The number below refer to the step number on the diagnostic procedure.

  1. 4

    The engine may also have a higher than normal idle if a vacuum leak is present.

    An exhaust system leak may be very small and cause the oxygen sensor to sense a false lean condition.

  2. 8

    When testing the circuits for continuity the resistance should be less than 5 ohms. When testing the circuits for shorts the resistance should measure infinite with all components disconnected from the circuit.
  3. 9

    This step determines if a base engine concern is causing the lean condition or if the lean condition is only present when operating on CNG.