I put in two new universal Bosch o2 sensors on my 97 850 wagon. These are the kind one has to splice in. I still get the 131, 135 and 137 codes after 50 miles or so. I've tried connecting a voltmeter to the black wire that comes from the sensors and gave it a proper ground. I've warmed up the engine, and tried raising the RPMs to about 2500. I get no reading however on either sensor. Has anyone done this test successfully? Especially on these universals? Am I doing the test correctly? I disconnected the 4-wire connectors and I am putting my positive lead on the black wire male pin. (I notice that in the other direction, from the computer, there is voltage from the car through the two white wires and the gray wire, but nothing through the black wire.