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keep in mind that the O2 sensor only generates anywhere from 0-1 volt, and averages around .5 volts. A poor or deteriorating electrical connection is not only frustrating but could also prevent this small voltage from reaching the computer and the gauge, too. Always be sure to check the electrical connections as well.

Testing the O2 sensor output is another way to ensure proper operation. A digital voltmeter can be used to test the output of an O2 sensor. WARNING! Be sure to only use a high impedance digital multimeter to measure the O2 sensor voltages. A conventional analog or low resistance meter can draw too much current and potentially damage the sensor itself. So, for testing, be sure to warm the engine to full operating temperature to shift the computer into closed loop. The sensor must be hot(at least 600 degrees or hotter) to operate properly. You may have to warm the engine at fast idle for 5-10 minutes with some cars to reach the target temp. Note that a few systems can drop out of closed loop at idle, so you may have trouble keeping the engine at a hot enough temp to see the readings you are looking for.

Just to reiterate, we STRONGLY recommend that when you make termination to the A/F ratio input wire on your vehicle that you solder the wires together, so that the connection is permanent, and also there is no potential for wire breakage or contamination of the signal transfer. PLEASE also be sure to test the signal wire BEFORE you solder the wires together, by twisting the wiring together; this will work for testing to ensure proper connection prior to the final termination.