I cannot locate the powertrain control module(PCM) in my 1991 Chevy S-10 Blazer.

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My Blazer started acting up after I replaced the heater blower motor. The Blazer will start and run till the engine warms up and then the spark dies. Once it cooled down it would restart. I replacer the ign. module with no luck. It also died when the door is shut hard. Once, it wouldn't start till I shut driver door. I checked all grounds that I found, all tight and clean. Help, where is the PCM????