RE: Dual EFIE Problem
Sorry for the delay. I re-arranged the forums a couple of days ago and forgot to subscribe to the new forum. I'm glad you also sent me an email to alert me to this.
First of all, a negative offset between a black and red test point should be impossible. Dumb question: The black test lead from your multi-meter is plugged into the black test point, and red into the red test point, correct? Another one: You are not using the same black test point to test against each red test point right? And a third one: The EFIE was on, right? With the red LED glowing? The two sets of test points are electrically isolated, and are as well isolated from their 12volt power source and ground. Therefore, it shouldn't matter what you're hooked up to, there should be a positive voltage at the rest test point with reference to the black. If it's not too much trouble, I'd like to test the EFIE with only 12 volts + on the red wire, and ground on the black. Then test the sets of test points. They should both read a plus voltage at the red test point with reference to it's black mate. If this is not the case, then the EFIE is faulty, and needs to be sent back to me. I'll replace it of course.
I almost didn't use black and red for the test point colors because it makes one think the black is a ground. It's not. It's just that it should be lower than the red test point, and should get the black lead from your meter. The black test point connects to the oxygen sensor signal wire. When you measure it vs ground, you're seeing the voltage produced on the oxygen sensor signal wire. This value should be oscillating between .1 volt and .9 volts or so, and if your meter has a slow refresh rate .45 volts as an average would be an expected reading.
The red test point connects to the computer, as you pointed out. However, it should be showing voltage. It should have the voltage on the black wire, plus the offset voltage being produced by the EFIE. I send these out with a preset offset voltage of .25 volts. Therefore, if you didn't turn the adjustment screw you should see .45 volts + .25 volts, or .7 volts when measuring the red test point vs ground. Of course you're supposed to see .25 volts between the black and red test points, but we know that's not happening.
The readings on the second sensor is probably OK. If the offset is .18 volt and you have .41 volt from the sensor and .94 volt to the computer, the math is pretty bad. But the trouble is you can't really read those fluctuating voltages very well with a digital multimeter, so those readings are within the realm of possibility of being fine. I'm assuming you're using a digital multimeter. If you have an old analog meter, with a needle, you might try hooking that up, and you'll see the voltages swinging back and forth a few times per second, and you'll see what I mean.
Ok, bottom line, it sounds like there's something wrong with the EFIE at oxygen sensor #1. Please do the test in the second paragraph above, and let me know what you see. If that test fails, we know the EFIE is a problem, and I'll get you another one.
If it pans out OK, then we'll need to look again at the wiring of that first sensor. Something is wrong there. You should be seeing voltage to ground from the red test jack.
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