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85 Turbo 5MT fried ECU

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  • 85 Turbo 5MT fried ECU

    Howdy so I have been having a limp mode issue with my 85 and I popped open my ECU to find that Scarface put his Cohiba out on my lower circuit board. Out of the 2 burnt capacitor things I go continuity between one of them and pin 113 which is FICD and body grounds. Got a new ECU on the way but I wanna make sure he donít put his cigar out on my
    circuit board again on this new one so I did a few test with my multimeter and not only am I getting a 4.3 amp draw but there is also continuity (with negative terminal removed) between my positive post and ALL my body grounds. Is this normal? If some kind fellow or madame could try this continuity test on their operative Z I would be glad to supply the kind individual with a pat on the back. If the info is of use, one of the capacitors say D801 next to it IIRC. Thanks for any help peeps

  • #2
    There will always be continuity between positive post and ground check the ohm's, divide 12v by the ohm's and you'll know how much draw there is.

    I had an ECU go out from water seeping into the ECU (previous owner removed the plastic shield @#$%!) and had to put a new one in.
    got a new ecu in, to only get "ECCS faulty" code from ecu and running on 3 cylinders. 100 man hours later, a new timing belt and all new sensors in the engine, it finally was a bad injector harness that really kept it from running right! I did the ear check thing as well and they were firing, but the short was just enough to make the injector signal week enough to not open all the way for the whole bank.

    Point of this story: get the FSM, go through at least the engine sensors and make sure they are all within 50% of spec (if the manual says 100kohm for something and it reads 50kohm, that's FINE) . It takes time, but it will save you the hard work I did replacing everything. If nothing is terribly wrong, you should be fine. I know the whole ecu loom goes down by the passenger footwell rocker and things can get rusty, so take a picture of that while you're at it.

    oh , and post a picture of your ECU please
    1984 GLL 300ZX NA to VG30ET Engine Swap Big Turbo
    1987 Auto Rare Kouki Slicktop Velvet-Cake (NA2T in progress: parts sourced)


    • #3
      Thank you for your help! I am gonna try that ohm test tomorrow for sure, but what does that draw tell me? To test for draws I usually remove negative terminal and check the amps between that and the negative post on the battery thatís how I found the ~4 amp draw which I was trying to track down last night with my brother watching the meter I was unplugging all the fuses and relays I could find one by one but that didnít lead to any results so I began unplugging engine connectors one by one to no avail either. I was just reading about the CHTS which has been my second suspect to the MAF so Iím going to grab my FSM and test that. I plugged in the new ECU last night to find that my problem persists . Wonít rev past 2K. Had to work on my other car so I didnít pull codes but Iíll get to that. I have continuity between all the MAF plug wires and their respective pins but what is weird is that the pin that is said to go to wire A on the MAF (pin 12 iirc) goes to wire F. I put the new plug in exactly how the factory one was so I donít know what to think there but I did find my old plug and put the wires into my new plug and hooked old plug to MAF (so that 12 lead to wire A vice versa) to no avail. I just did the timing belt but Iím going to check the CHTS and retest my junkyard and Autozone MAFís maybe I missed something. Thank you again for your help!
      Last edited by Student005; 04-15-2019, 08:42 AM.


      • jy1235689
        jy1235689 commented
        Editing a comment
        Then you already have the draw measured. I was just pointing out another way to do it if it isn't safe to hook up a battery. 4a x 12v = 48w. Idle amperage shouldn't be that high.