Code 25, O2 Circuit/Lean Exhaust Indicated

WARNING: This page is about a different car, the 1991 Geo Prizm. However, it is still accessible from the selected car via links, so may be relevant.

ECM supplies approximately .45 volt between ECM terminals OX+ and OX1. If voltage is measured with a 10-megohm DVOM, reading may be as low as .32 volt. The O2 sensor produces a varying voltage as engine reaches normal operating temperature. Voltage will vary from .1-.9 volt. The O2 sensor does not produce a 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.

Code 25 will set if O2 sensor signal voltage on Red wire remains less than .2 volt for one minute or more with system in closed loop.