10-4, I seem to recall something about possible wire corrosion by the battery, as that's where the computer is. Though it might be FWD vehicles of that era I am thinking of. Not trying to steer you wrong, but it's been a while.

Try wiggling the wiring around and see if the signal changes, that would indicate an intermittent issue.

I browsed Rockauto to see if they had a computer for you, no California emissions with an auto listed. They have Cal with a stick and Federal for both.