I talked to my cousin last night and he said that he and a friend did the knock sensor about 4 months ago (Cousin = previous owner). So now I'm just completely lost... unless it went bad that fast...

Connector come loose? Wires damage from improper routing? Scantool?

Anytime that I have checked a knock sensor is with using a scan tool, monitoring the engine timing, and a hammer. I would simply rap on the engine block with the hammer and watch the engine timing change. The knock sensor is simply an output sensor. It is actually a piezo-electric output device. As this material is strained (i.e. an engine knock), it outputs a very small voltage to the PCM. The PCM reads this signal and proportionately retards the timing to prevent the knocking. In all the years that I have worked in the garage I have never replaced a knock sensor nor have any of the other guys unless there was a damaged connection or wire. I am going to do a little more research on that code 43?. It may be the ESC itself not reacting properly to the engine knock. I will get back to you.

PS I have simply rapped on the engine block with a hammer and listened for an RPM change (because of the engine retard). It is quick to do and may help.

and you tried this at idle? or off idle?

i dis agree i changed a knock sensor on a 90gp 3.1mpfi curd the problem

What are the chances of this happening.... Here I am giving advice about a particular problem and guess what....

Engine has been lacking in power lately and my fuel economy has gone horribly down when the engine is up to temp. So I figured I would wait a bit to get a more concrete symptom to show up so I could diagnose it easier. Check engine light started coming on and off last week. Well today I figured I would get out my trusty paper clip and have a look. Well, code 43 showed up....ESC just like my friend. Same symptoms as well.

My alternator has been chuckling pretty badly when it gets hot. I am just wondering, because the alternator is located close to the knock sensor if the knock sensor is picking it up and retarding the timing because it believes the engine is knocking.

Have you figured your out yet, because that could save me a bunch of time.

Thanks for now.