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Can a questionable ground kill multiple 7730 ecms?

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  • Can a questionable ground kill multiple 7730 ecms?

    I am fighting with a 7730 swap in a 86 SC camaro. I was checking the wiring tonight because the flow chart below says that less than .6 volts at the O2 sensor is a bad ecm. All 3 of mine are .37 to .39.
    Upon checking the grounds I found a .67 ohm resistance at 20k ohm settings on the ground wire I used for the ECM grounds. Could that have fried my ecms?


  • #2
    thats a lot of resistance in a ground circuit. depending on what the ground is actually for in the ecm, yes it could be responsible for damage to the ecm. i would fix the ground circuit and retest the o2 sensor circuit.

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    • #3
      It is the wire connected to the 4 main chassis grounds. I ran a temporary wire directly to a ground stud I installed but it didntbchange the voltage readings from any of the 3 ecms.

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      • #4
        the thing with an ecm is if it has a poor ground it has a habit of finding a ground path through whatever circuit it can, and that could have been the 02 sensor circuit in this case. for testing i would go directly to the battery with that ground wire.

        i had a similar issue with a car i put together last year, i had a ground stud beside the battery and i had the ecm , coils, water/meth system all grounded there, and a 4ga ground to the battery. the 4ga, brand new off a roll had a corroded spot in the middle of it and created high resistance. it was all fine under light load, but once the water/meth system went over 50% duty cycle it would shut off, it would start having crank signal issues and scattering the timing. turns out the water/meth system was trying to ground through the ecm, and it picked the crank sensor circuit. the car ran ok after it was fixed, aside from a crank sensor glitch at the same rpm every time. it looks like its cost me a $850 ecm.

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