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Where art thou Art (Benstein near Baltimore)? 200 1992

posted by  Philip on  Wed Jan 30 11:14 CST 2013
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last visit: Thu Oct 23 10:21 CST 2014
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Help! I am at a loss to figure which way to go with my ECT anomaly.

Looking at the diagram, it appears that neither of the two red/blue wires from the connector at the ECT are grounds.

It response to your questions:
Original measurement: probe on the back of #5 (black) and other probe on #13. Connector connected to ECU, ignition switch to position II.

#5 to chassis shows it is grounded.

Removed connector from ECU. Ignition switch to position 2. Voltage from 5 terminal to 13 shows 6 v.








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    Where art thou Art (Benstein near Baltimore)? 200 1992

    uid 18083's pic
    posted by  lucid on  Wed Jan 30 12:03 CST 2013
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    last visit: Fri Oct 24 12:31 CST 2014
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    "Looking at the diagram, it appears that neither of the two red/blue wires from the connector at the ECT are grounds."

    That's correct. The ECT has two sensor elements, both of which share a common ground via the sensor body's thread contact with the head.

    One sensor red/blue wire goes to FI ECU 13 and the other to the EZK Ignition CU terminal 2.

    --
    Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.








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      Where art thou Art (Benstein near Baltimore)? 200 1992

      posted by  Philip on  Wed Jan 30 12:48 CST 2013
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      last visit: Thu Oct 23 10:21 CST 2014
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      Thanks for the reply, here is my situation:

      The car dies from idle if you give it gas until it warms up. The codes say it is the ECT. I replaced the ECT sensor with a URO. No change.

      I then back measured from terminal 13 to 5 and got 6.05 volts with the ignition switch on. With the connector unplugged from the ECU, I got 8,200 ohms between 13 and 5.

      So does this point to digging into the wiring harness below the 2 and 3 intake manifold and looking for the cold joint on the ground (described by a post on the Brickboard), or looking elsewhere?

      Any help would be greatly appreciated.








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        Wherefor what? 200 1992

        uid 27's pic
        posted by  Art Benstein on  Wed Jan 30 17:56 CST 2013
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        last visit: Fri Oct 17 20:10 CST 2014
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        Hi Philip,

        I see by a second (or third) thread you've started, you've abandoned this line of investigation for the parts swapping method. In that case, the good used part vs. the out-of-box new part failure. You say it is resolved.

        Anyway, your response to my question about your measurement method is not clear on the point of how you measured 6.05V.

        You say "Removed connector from ECU. Ignition switch to position 2. Voltage from 5 terminal to 13 shows 6 v."

        If the connector is removed from the ECU, what are you putting your probes to? The unplugged connector?? The ECU pins??

        The voltage measurement is made with the connector in place. Plugged in. No other way to do it. Resistance (of the ECT) is measured with the plug and ECU separated.

        If you did indeed measure 6.05V between 13 and 5 with the ECU connector in place, then you have some more digging to do.

        --
        Art Benstein near Baltimore

        He had a photographic memory that was never developed.








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          Wherefor what? 200 1992

          posted by  Philip on  Wed Jan 30 18:36 CST 2013
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          last visit: Thu Oct 23 10:21 CST 2014
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          whoops, I misread your suggestion to read the voltage with the ECT disconnected, I read it as the ECU disconnected.








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            Wherefor what? 200 1992

            uid 27's pic
            posted by  Art Benstein on  Thu Jan 31 10:58 CST 2013
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            last visit: Fri Oct 17 20:10 CST 2014
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            The only way I can explain the 6.05V is you are reading what most folks call a stray voltage, or leakage current, from a circuit which is for all practical purposes an open circuit (the open URO sensor). Meters these days are sensitive enough to see the current conducted by a damp insulator, or even your own skin.

            Using voltage to troubleshoot an ECT, you must backprobe the connector, either at the ECT (very awkward) or at the ECU, and everything needs to be plugged in when you take the reading, so you see the voltage in a working circuit.

            This is entirely opposite to using resistance to "test" the ECT, when you must disconnect and turn off the power. This is pretty much a hard and fast rule you can depend on: resistance measurements are made with the power removed, and voltage measurements with it connected and in-circuit.

            Sorry to have led you "astray."
            --
            Art Benstein near Baltimore

            A boiled egg in the morning is hard to beat.







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