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2G Sensor Wiring Problem

Posted by Eduardo Zibetti, Jul 12, 2020

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  1. Eduardo Zibetti

    Eduardo Zibetti Probationary Member

    Joined Jul 12, 2020
    Passo Fundo, South America
    Hey guys, i'm new on the forum and brazilian, so my english isn't perfect LOL.
    I have a problem with coolant temp sensor, as u can see in the image below:

    (i've tried to upload but doesn't work, so i post the links)

    They are working perfectly, but sometimes (more than i've expected) the sensor oscillate and the CLT goes to 230ºf in 0.1s, then back to normal (192ºf).

    I change the CLT sensor and the problem persists.
    I have an aftermarket ECU in the original wire (plug n play megasquirt MS2), but with original ECU (with ecmlink) I already had the problem.

    There are images of my original wiring. Three white wires going into green sheeths. These wires go to pins 75, 76, and 78 (Front O2, Rear O2, and Knock Sensor).
    There are also 5 black wires (one of which is pin 92 [Sensor Ground]) that are coming from the wiring harness, through the green sheeths, and then the all of the black wires are soldered back to the sheilding inside the sheeths.

    My problem is these wiring? Anyone can help me?
    Thank you and sorry for the gramatical errors LOL
  2. Buddy2

    Buddy2 Proven Member

    Joined Oct 7, 2013
    Helsinki, Europe
    Electrical problems are pain in the... have you measured resistance in that coolantwire between the ecu connector and sensor? You have new sensor and ecu so problem is likely in wiring? If you shake wires while logging can you get any spikes?

    346  9

    1992 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM

    152  0

    1992 Mitsubishi Eclipse GSX
    manual · 1G DSM

    631  8

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    frosh29 and Kryndon like this.
  3. Eduardo Zibetti

    Eduardo Zibetti Probationary Member

    Joined Jul 12, 2020
    Passo Fundo, South America
    I will measure the resistance, dont meansured yet.
    If i shake wires while logging nothing happens...
    So I suspect ground wires...
  4. Widgmaster

    Widgmaster Supporting VIP

    Joined Aug 24, 2018
    Sarnia, ON, Canada
    I can not reply to your wiring issue but want to say your English is better than some of the English born people I know.. Your grammar is fine brother

    68  1

    1977 Glastron Aqua Lift
    awd · automatic · Misc Vehicles

    110  1

    2002 Dodge Dakota Extended Cab
    rwd · automatic · Misc Vehicles

    287  10

    2001 Mitsubishi Eclipse Spyder GT
    fwd · automatic · Misc Vehicles
  5. Eduardo Zibetti

    Eduardo Zibetti Probationary Member

    Joined Jul 12, 2020
    Passo Fundo, South America
    haahaaa ty bro :)
  6. luv2rallye

    luv2rallye DSM Wiseman

    Joined Jun 7, 2003
    Minneapolis, Minnesota
    Important note: On a 2g (but not 1g) ECU pin 92 (note: this pin is incorrectly labeled Ignition switch on some 2g ECU pinout diagrams) goes to the signal grounds of the following engine sensors: manifold diff pressure, engine coolant temp, front O2, rear O2, TPS, volume air flow (MAF), and on the 98 & 99 fuel tank diff pressure. Pin 92 is grounded inside the ECU but all these sensors signal grounds must NOT be grounded anywhere but through pin 92 to avoid electrical noise and ground loops from affecting the sensors differential signals and to guarantee that the sensor's ground is at the exact same voltage potential as the ECU ground (which it might not be with large current flowing through any other ground). Some people and even some mechanics, don't know/realize this and they mistakenly connect signal ground to the engine (as in a 1g). A typical example is when replacing the front O2 sensor and the harness connector/wires are damaged and need replacing. Connecting the O2 signal ground to the engine/chassis (or even battery negative) can cause misleading and noisy signals to the ECU causing the ECU to run the engine poorly. And if it is still also connected to the original harness signal ground wire, then all of the above engine sensors will also have that problem.

    3K  0

    1999 Mitsubishi Eclipse GST
    14.200 @ 95.000 · 2G DSM
    motomattx likes this.
  7. Eduardo Zibetti

    Eduardo Zibetti Probationary Member

    Joined Jul 12, 2020
    Passo Fundo, South America
    In my case, only the CLT sensor have problem.
    I use an ECU with internal MAP sensor and wideband, so I dont use front/rear O2, manifold dif pressure and MAF wires/plugs.
    I use CLT and TPS connected to ECU, but the TPS is fine, the problem is only in CLT.
    I will remake the ground wire of these sensors and test, so I come back here and give a feedback.

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