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2G [Last Question] ECU Wires help

Posted by Echosyp, Jan 25, 2020

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  1. Echosyp

    Echosyp Proven Member

    43
    26
    Joined Oct 31, 2019
    Clanton, Alabama
    Just got off work and it's decent outside so I was looking over the last few things.

    ECU Wiring.

    Far right plug of ECU has one of the white wires skinned back and another wire taped to it, but the wire goes nowhere, either on purpose or came loose.

    Looking on the wiring diagram, shows 3 white wires over there, Front O2 Sensor, Back O2 Sensor, (95-96 Knock Sensor).

    When I got the car one of the AEM gauges had a white wire laying in the floorboard. Owner said his big ass foot snatched it out and he didnt know where it went, so he left it. Car has AEM air/fuel gauge and AEM boost gauge.

    Car also has IAT and Map sensor installed for speed density, but they arent wired up.

    So any idea where the wire coming from the ECU would go? And the white wire from the gauges? Not sure if it's the boost or A/F gauge wire.
     

    Street Build 238  2

    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  2. Kryndon

    Kryndon Proven Member

    406
    232
    Joined Jan 10, 2014
    Bulgaria, Europe
    I think you're on the right track with the AFR gauge. When I did my Innovate wideband install recently, I saw that if you wanted to simulate a narrowband or incorporate the install for ECU control software such as ecmlink, you splice into the white front O2 signal wire. So that would mean the default wire should go to the front O2, which was 4 wires coming from the sensor. Is your front O2 working?
     

    Street Build 3K  12

    1997 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  3. Echosyp

    Echosyp Proven Member

    43
    26
    Joined Oct 31, 2019
    Clanton, Alabama
    Not sure if it's working or not, does have check engine light on and he said when he ran the code it was O2 sensor, but he claimed it was because the flex pipe is damaged because the car sits so low, so it has a huge leak, but has a deep rumble sound so he never had it fixed. Then he said his foot pulled the white wire loose coming from one of the gauges and he didnt know which gauge it was or where it went.

    My A/F gauge sits on 14.8 and never moves, I was thinking it was because the sensor is installed behind the flex pipe and the leak is causing it not to work.

    Also didn't wanna hook the white wire up to the ECU wire and fry anything.
     

    Street Build 238  2

    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  4. Kryndon

    Kryndon Proven Member

    406
    232
    Joined Jan 10, 2014
    Bulgaria, Europe
    I'd take my bets and say the white (signal) wire to the front O2 (or possibly rear O2, whose wires go under the center console) is severed and not carrying a signal, resulting in a CEL on. This would further be validated by the constant 14.8 that the gauge is reading (although you should double check what the standard values for an AEM AFR are when it's not fully reading).

    The "he said" and "he did" are common. I've heard them myself. Whatever the reason, he didn't fix his sh** when selling you the car, nor does he seem too bothered about the state of the car and how it operates.

    Get the electrical manual opened up again and start probing the white wires to check continuity to figure out which wire you've got exactly. Alternatively the manual should say exactly to which sensor that specific pinout goes to. But you can also manually trace it by using a voltmeter to measure ohms from one end of the wire to the connector (harness side) at the front O2. If that doesn't ring, check the rear O2 connector under the center console; it is a 3 wire sensor if I'm not mistaken.

    Additionally, run a simple diagnostic and see what the code is for exactly. It should specify rear or front. Also I'd like to add that, even if there's a huge leak before or after an O2 sensor, the wideband reading should still give some readings different than 14.7 (if it's connected properly, of course).

    Also how the hell did his foot rip a wire out?! He must have done one shoddy wire job if he had wires hanging so low as to catch on his foot. My guess is he's just bullshitting you for some reason.

    Anyway, go over the wire, referencing the manual if you can, and trace it. Determine if you have an O2 wire severed, then solder it back together. When that is done and you start getting some readings on the AFR gauge, attempt to fix your leak to get the readings back in check.
     

    Street Build 3K  12

    1997 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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    Echosyp likes this.
  5. Echosyp

    Echosyp Proven Member

    43
    26
    Joined Oct 31, 2019
    Clanton, Alabama
    Ok here's what I got.

    Both O2 sensor wires are good.
    O2 front is the one skinned back and has a brown/pink wire attached to it that looks like it came loose somewhere so I taped the end up for now.

    On top of the ECU rolled up was 2 sets of wires coming from the firewall, I traced one back to the MAP sensor, the other I traced thru the firewall on the engine side, but it turns and goes under the car toward the back. So unsure what else they was going to hook up to the ECU.

    The gauges are AEM gauges with

    Red, Black, White, Blue wires.

    Both red wires are hooked together and plugged into the fuse box.
    Both black wires are hooked together and grounded to the body under the dash.
    Both blue wires are taped together running nowhere
    One white wire is taped up with the blue wires going nowhere.
    Other white wire is the one he said he ripped out with his foot, its rolled up and tucked under the carpet in the floorboard. So unsure where that one goes, and guessing it's the Air Fuel white wire.


    He bullshitted a good bit on a few things, said the passenger side window motor was burnt out, turned out the window lock button was just pressed. Told me the AEM boost gauge wasnt hooked up and the wires was laying in the glovebox, I pulled the boost gauge out and it was just unplugged. Plugged it in and it worked. Not sure where exactly the factory boost gauge is hooked up at, but it also still works along with the AEM one.
     

    Street Build 238  2

    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  6. tk106

    tk106 Supporting Member

    2,279
    723
    Joined Sep 11, 2017
    Cincinnati, Ohio
    Best thing to do is check all the wiring and not put your focus on the one loose wire. It’s going to take you a good amount of time. The wideband does have an output that you can wire in to log. Do you have ecmlink? If so, go to links page and see which wire to tap into on the harness.
    Wideband should not be fixed on one number except when your wot and getting into boost.
     

    254  3

    2000 Jeep Cherokee Sport - Classic
    awd · automatic · Misc Vehicles

    247  4

    93 Civic 4 Door -sold-
    fwd · manual · Misc Vehicles

    Street Build 2K  6

    1992 Eagle Talon TSi AWD
    12.625 @ 111.42 · 1G DSM
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  7. Echosyp

    Echosyp Proven Member

    43
    26
    Joined Oct 31, 2019
    Clanton, Alabama
    Reading on AEM site 14.7 is what it stays at if the sensor is unplugged or a wire is broke or the sensor is bad. I'm gonna have to just find a place to jack it up and check everything.

    I did go out and mess around with the wires and now when I crank the car up it jumps up to like 16.8 then back down to 14.8 soon as the car cranks.
     

    Street Build 238  2

    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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