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Dual EFIE Problem
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Hybrid Offline
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Post: #1
Dual EFIE Problem
Hopefully this isn't a big deal but I installed my dual efie on my Civic Hybrid which has two O2 sensors, the first in the first 3-way catalyst and the second downstream of the second 3-way catalyst. Both are four wire connections and with the factory service manual, quite easy to figure out which wire is which. The green and white wires are associated with the first O2 sensor and I have verified the connections. When I plug a multimeter into the first set of test points, I get negative offset voltage. Testing from the black test point to ground gives me .45v at idle. Testing from the red test point to ground gives me no voltage to the computer. The second set of test points gives .18v offset. The second black test point shows .41v to ground and the second red testpoint shows .94v to the computer. I also got a DTC of P0139 (slow response from O2 sensor 1). There are 3 sensors on this car but I am ignoring the wide-range air/fuel sensor because I am not dealing with it. Any ideas??
09-25-2007 09:17 AM
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mike Offline
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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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09-25-2007 07:22 PM
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Post: #3
RE: Dual EFIE Problem
I did read the installation and I do realise that the black test point isn't ground. I actually used the vehicle ground via the power plug (cigarette lighter). As I understand your instruction, I need to disconnect the leads to the O2 sensors and test using the red and black leads only. Red to 12v and black to ground. Can I use a jumper wire for black and red at the connector? disconnecting the O2 sensors is kind of a pain otherwise. I will try this sometime today and get back to you. Thanx
09-26-2007 04:43 AM
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mike Offline
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RE: Dual EFIE Problem
Yes, absolutely. Just unplug the EFIE, and jumper power to the plug pins that the red and black wires are connected to. Thanks.

I'll be keeping an eye out for your reply.

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09-26-2007 10:50 AM
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RE: Dual EFIE Problem
Ok. Here's what I got. With just the red and black hooked up, I get .25v offset between the test points. With the red probe from my DMM connected to the black test point and the black DMM probe connected to vehicle ground, I show -.28v. With the red DMM probe connected to the red test point and the black DMM probe to vehicle ground, 0v.
The second test points show .11v offset and 0v to ground from both test points.
09-26-2007 01:31 PM
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mike Offline
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RE: Dual EFIE Problem
Ok. If I understand correctly, the EFIE is working properly. To verify: you have unplugged the EFIE and jumpered 12 volts to the red wire (of the EFIE), and ground to the black. When measuring between the first set of test points, you get a plus .25 volts. This is with your red and black meter probes plugged into the same color test points. If all of this is correct, then the EFIE is working properly.

So, we have to check the wiring of that first circuit. Going back to your first post, one possible explanation comes to mind, and that is that the wire you think is going to the vehicle computer is actually going to ground. You reported 0 volts from the red test point to ground. This could also explain a negative reading at the test points when it's plugged in, but a positive reading with your recent test with only the power hooked up.

As a note, I have had experience with the manual showing incorrect wire colors. It's probably rare, but you can't bet your life on what the manual says. I can't see your particular vehicle, but do what you can to verify the wires that your white and green are connected to.

I'll be checking my messages frequently.

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09-26-2007 01:47 PM
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Post: #7
RE: Dual EFIE Problem
Which pair of wires do I focus on; green & white or brown & blue?? It's not real clear. The problem side is opposite the on/off switch.
09-26-2007 04:27 PM
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mike Offline
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Post: #8
RE: Dual EFIE Problem
Ooooh. That's the brown/blue pair. The green/white is for the EFIE closest to the switch as you have surmised. My mistake. I thought you were having trouble with the white/green circuit.

Are the rest of my assumptions in the last email correct?

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09-26-2007 05:27 PM
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