951 Oxygen Sensor
With the TPS working correctly, I can move on to checking some other things - like the oxygen sensor. There's some pretty good instructions over at Clarks-Garage.com on this sort of stuff, so naturally I try to learn what I can there and from posts on Rennlist. In order to read its output, you must make an "in-series" reading; meaning you have to have the sensor connected and the engine running and then at the same time tap into the wires.
You might be able to connect your meter to the back of the DME connector or perhaps you can slip the end of a bent paper-clip into the joined, O2 sensor connector and read the voltage there.
In this way, the tap wire could provide a way to read the voltage coming out of the 02 sensor.
Generally, I think there are two tests that I wanted to perform. First, to just verify that the O2 sensor was active (not dead) and second, to verify that the sensor is responding correctly. The first part is pretty easy, the second part means introducing propane or some sort of vacuum leak to alter the air fuel mix.
So just to find if the sensor is active, I disconnect the plug to the DME and "tapped on" a test point to pin 24 of the harness. With that test lead, I can run the engine and measure the O2 sensor's output voltage that is being provided to the DME. I will hook up a Air/Fuel ratio meter to this someday, for now, I can see that the o2 sensor is active (varying from 0 (lean) to .89 (rich).
Update: Since this time I have installed a narrow band air/fuel gauge (really it is just a small, seven element, LED pack that indicates voltage level). After an hour or so to install this little device and about 3 minutes of starring at the flickering lights I realize this is an an irritating little POS and I wish I had never seen the thing. It does; however, replace the clock, which is also a POS. If I could do it all over again, I think I would go for something a bit more classy, like a piece of black electrical tape trimmed to cover the clock face - now where did I put that exacto knife...;]