Diagnostic Aids

WARNING: This page is about a different car, the 1992 Geo Prizm. However, it is still accessible from the selected car via links, so may be relevant.

Normal sub-oxygen sensor voltage varies between .1-1.0 volt while at normal operating temperature. Code 27 sets in one minute if sensor signal voltage remains between zero or one volt.

Ensure connection to Brown wire is clean and tight. An open in the Brown, White or Black wire will set Code 27. If Code 27 is intermittent, see TESTS W/O CODES article in this section.

Fig 1: Code 27 Schematic (Calif. GSi), Sub-Oxygen Sensor Circuit Open Or Shorted Circuit

Fig 2: Code 27 Flow Chart (Calif. GSi), Sub-Oxygen Sensor Circuit Open Or Shorted Circuit