Getting the codes read using a scanner can provide a little more info than you get from counting the blinks of the Check Engine Light. But the only information the PCM can give you, is what ever the sensors report to it. There isnt any sensor that will tell you that you have a bad/corroded wire in the wiring harness where it runs behind the motor, or that the target magnet in the end of the camshaft has gotten weak. Both of these might show up as a CPS signal not found during cranking, or some such result.
I had the ASD relay code showing up with my 97 when we got it. It would also quit running when making right turns - unless you took them very very slowly. That problem went away after I pulled the engine, so I could get to the engine wiring harness, and replaced twelve of its wires that were melted together, near where the harness went past the exhaust manifold.