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Testing bias 02 voltage. Both pre cat 02 sensors stay at 450mv on scan tool. Test light lights between power and ground for 02 heater circuits. Test light to ground koeo touch signal wire 02 bias voltage stays at 450mv on scan tool. Going to use dmm to see if bias voltage is at 02 signal wire connector. Going to measure dmm between signal and sensor ground. Service procedure calls for the one test above I did to take jumpers and disconnect the 02 connector and jumper the signal wire to ground and also jump the sensor wire to ground also. My question is what does jumping sensor ground wire at same time jumping signal wire to ground do? I used a test light connected to ground touching signal wire watching the scan tool. Is this a good test without the sensor ground wire grounded also? Thanks.
The sensor ground might be biased as well, in other words sensor ground ain't chassis ground. If so, this was "corrected" when pulling sensor ground down by the recommended test procedure....
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Jumping the signal to the signal return tests the signal and ground wire integrity at the same time. Your next step should be to measure the signal at the PCM and then ground it there. Also, remember, scan data may not update on an O2 data PID with the key on only. Crank it or start it when you are doing these tests to be sure.
Thanks for the reply. I planned on checking with dmm the signal and signal return to make sure it is getting to the 02 sensor itself. I used a test light to ground and touched signal wire scan data stayed at 450mv on scan tool. Didn't know why service procedure said ground both the signal and the return at 02 connector while watching scan data. Thanks for the help.
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