Re: possible bad ECM need help...??
Fan could be coming on from the high temp sensor instead of computer control. 2 things I'd check first are grounds and verify no ripple voltage in the system (AC voltage leak through rectifier bridge in alternator). Grounds are easy to check, as is the ripple voltage with a good DVOM. An quick check to see if the rectifier bridge is on its way, is to unplug the alternator field connector and see if the driveability/running gets better. Don't drive too far like that as it won't be charging the battery. Unfortunately, this check can also mask a bad ground so verify proper grounds to the body, engine, and ECM first. You can plug a 1k ohm resistor into the coolant temp sensor connector and see if the computer reads a steady temp to verify the sensor itself is ok.
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67 Camaro Traded for my 98
68 Camaro Street/Strip
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