Diagnostic Procedures

Verify clean, tight connection on G106 (Brown wire). Check HO2S heater operation. See SYSTEM/COMPONENT TESTS - 1.8L article. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM 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 27 Schematic (Prizm 1.8L - VIN 8) (Calif. Emissions) Sub-heated O2 Sensor (SUB-HO2S), Open Or Shorted Ckt

Fig 2: DTC 27 Diagnostic Flow Chart (Prizm 1.8L - VIN 8) (Calif. Emissions) Sub-heated O2 Sensor (SUB-HO2S), Open Or Shorted Ckt