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Diagnostic Aids

Verify clean, tight connection on G106 (Brown wire). A lean air/fuel condition may be caused by contaminated fuel, low fuel pressure or vacuum and exhaust leaks.

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out, improperly mated, broken locks, improperly formed, or damaged terminals, and poor terminal-to-wire connections before component replacement.

Fig 1: Code 25 Schematic (Except LSi) Oxygen Sensor Circuit, Lean Exhaust Indicated
G93B78817
Fig 2: Code 25 Flow Chart (Except LSi) Oxygen Sensor Circuit, Lean Exhaust Indicated
G93C78818