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1999
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4Runner Base, 4WD
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Repair and Diagnosis
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Engine Performance
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Engine Control System Self-Diagnostics - 4-Cylinder
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Diagnostic Tests
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DTC P0420: Catalyst System Efficiency Below Threshold
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Notes
DTC P0420: Catalyst System Efficiency Below Threshold: Notes
NOTE:
Heated oxygen sensor No. 1 refers to oxygen sensor closest to engine block. Heated oxygen sensor No. 2 refers to oxygen sensor farthest from engine block.