Code 25, Oxygen Sensor Circuit Lean Exhaust Indicated: Notes

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.

O2 sensor produces a varying voltage as engine reaches normal operating temperature. Voltage will vary between .1-.9 volt. O2 sensor will not produce voltage until sensor reaches 600°F (316°C). When sensor is less than this temperature, an open loop condition exists.

NOTE: Test numbers refer to test numbers on diagnostic chart.

This checks for an intermittent Code 25. Code 25 sets when O2 sensor signal voltage on Black wire remains below .2 volt for one minute or more with system in closed loop.