According to my manual, the way to test a knock sensor on a 1992 3.1L V-6 is to check the resistance. It should read between 3300 and 4500 ohms.

Where do I place the contacts? I assume one on the engine block and one on the center electrical connection of the Knock Sensor?

If this checks out okay, I was told to check the voltage of the lead going to the Knock Sensor. I assume that I place the one lead on the engine block and one on the wire that runs to the Knock Sensor with the ignition in the on position, is this correct?

The reason I am testing this is because I occasionally (seems to happen only after the vehicle is idling a long time) the "Check Engine" light flashes and stays on on for a little while before turning off. The scan showed a Code 43.

Thanks!

By the way, I did notice that the wire plugging in to the Knock Sensor had some black electrical tape wrapped around it, so maybe it is an intermittent short in the wire? I drove it for 25 minutes last night on the highway and the check engine light never came on. The car runs great with plenty of power.

 

That troubleshooting is correct. From the body of the sensor to the center pin for the resistance check. This is with the connector disconnected.

The connector pin to the engine block should be +5 volts with the key on and the connector disconnected. This same measurement with the connector jumped to the sensor should be about 2.5 volts.

That is what the ECM is looking for. The sensor divides the +5 volts in half which the ECM is checking. If a lot less then 2.5 volts, or a lot more then 2.5 volts, and the ECM tosses code 43.

An intermittent wire, sensor, or connector will cause this.

RBob.

 

Thanks, hopefully I will get this figured out!

 

I removed the starter last night so I could get to the Knock Sensor easier. I ran an ohm test from the center of the Knock Sensor probe to the body of the knock sensor and it read 3. 89 set on 20K on the ohm meter. I believe that means 3890 ohms and that means my Knock Sensor is within specs. I then set the meter on Volts DC at 200m and with the sensor unhooked and battery unhooked I tapped the engine block and the meter read anywhere from 2 to 4. 0 at each tap. I beleive this means the Knock Sensor is good. It does have some of the rubbber coming out from around the center area, but I just pushed it back in.

I then inspected the pigtail connection going to the Sensor and noticed an area where someone had spliced in a small section of wire (about 4 inches long) using standard household electric wire (the kind you would wire your 120 electrical outlet in your house with). They used a butt connector and when they crimped the butt connector the plastic cracked a little. Also the plastic connector to the Sensor had a small chip out of it. Im thinking that is where I may have been getting the intermittent code? I replaced the butt connector and wire with a new pigtail and soldered in to the purple wire and then used heat shrink tubing to cover it.

Thats as far as I have gotten so far. Hopefully that in itself will have solved the problem.
When I hook the battery back up and start it, I was told that the computer would have to "re-learn" the idle settings and other specs. I was told that the car would run rough for several days before everything goes back to normal. Is this true?

 

Most certainly does sound like you found the problem (POS: previous owner syndrome).

As for the idle learn, it should be done. Otherwise the engine will tend to stall and surge. Isn't too bad with a stock trans, but with an auto trans it is hazardous. There is a thread or two on the V6 board here.

Use the advanced search and: drop 'idle learn' into the search key words and my username into the user box.

RBob.