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1994 roadmaster bad ecu or opti (help)

Diesel91

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Hello everyone. I am new to the forum. My mom has a 94 roadmaster that's been acting like it has a really bad misfire, but when i plug in my scanner the cooling fans kick on and the speakers start making this pulsating sound. I am not used to scanning older cars like this so I am leaning towards the ecu but would like other opinions if anyone has had similar issues. thank you
 

Diesel91

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I also bought a gm 0bd1 scanner, it does the same thing and no code lights flash at all but if i switch the scanner to abs the fan turns off and the speakers stop making noise and the consol flashes code 12 system ok
 

HotZ28

Full Member
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Buick Ownership
1996 Roadmaster Limited Collectors Edition 58k - 1996 PAU
Welcome to the forums! When you hook up a scanner to an OBD-1/OBD1.5 system, the fans should turn on. That was how it worked back then. If you go to ABS mode, that is communication from the ABS module, not the PCM. You could very well have an OPTI/ignition wire issue and if so, the plugs will foul out! I just changed the water pump, OPTI, plugs & wires on my '96 RMS about 8-months ago and it still runs like a raped ape.
 
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