The ignition output signal is that circuit used by the ECU to tell the ignitor to fire the coil. I don't have a wiring drawing right now, so can't tell you what wire color. Look for dirty/loose/corroded connection at the wiring harness plug for the distributor.

It could explain your occasional non-starting too.

Don't do anything for code 43 (yet). There's a fair chance that code will not come back after you get the new O2 sensor and cleaned up the trigger circuit for the ignitor.