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Re: GM C3 question..is Diagnostic Mode hardwired in ECM?
Posted to Technical Discussion Forum on 5/18/2003

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Hi Allen,

Two things I would check first off, 1) Is the ECM the correct part number? IIRC, there were only two PNs for ECMs in 81, with ISC and without ISC. 2) Is the tach lead connected to coil neg... Login to read more.