Truck Repair: bad knock sensor?, sensor circuits, gmc 3500

Question
Hi.
I have a 93' GMC 3500 that was having power trouble, I replaced the Egr, O2 sensor and the
muffler and have gotten back most of my power.
I also changed my knock sensor. I am now getting a service engine light with the codes for the knock sensor, I exchaged the sensor with another one and disconected the battery to clear the code but I am still getting the code. I think I might have screwed up in that I tested the wire with a circut tester? Could I have did something to the ECM?

Answer
Well, those sensor circuits are designed to work on about 5 volts, and just milliamps, which are thousandths of an amp. A test light draws considerably more than that, and would act like shorting that wire to ground.
A quad driver is what i believe they call it, which I believe is one of four transistors.
So although it is possible you didn't cause any damage, the answer to your question is yes, you could have.

As for all the tests, check the fuel pressure.

Van