Diagnostic Procedures

Verify clean, tight connection on G106 (Brown wire). 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 terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

Fig 1: DTC 21 Schematic - Federal Emissions (Prizm 1.6L VIN 6) O2S, Open Or Shorted Circuit

Fig 2: DTC 21 Diagnostic Flow Chart - Federal Emissions (Prizm 1.6L VIN 6) O2S, Open Or Shorted Circuit