Hi Matt, My name is Edgar, I have been watching your tutorial videos basic electrical for beginners and I happen to have a P0300 code on my 2000 Chevy Astro, the truck runs pretty rough and nearly dies at stop signs I have checked several variables including the long term trims which shows both banks are lean at 25/28 at idle, i checked fuel pressure and maf which are ok and now I happen to be trouble shooting the EGR valve and every thing have tested ok on all A B C D connector wires except power circuit wire (E). when I back probed wire E being disconnected from the EGR with my DVOM set on DC mode, key on but without cranking engine, my dvom read 11.83 Volts but when I back probed it connected to the EGR valve the meter read 85.9 mV.
Do you know if this is normal or the test results mean if wire E is short circuit or is it possible the egr is shorted to ground within it’ s circuit?
I also probed this same power circuit with a computer safe circuit test lamp which also indicates polarity, so I connected it between battery positive and power circuit wire “E” with harness connected to EGR valve and the test light lit green as if it was making contact to ground! Weird, test lamp should not have lit on at all.
Next back probed with test lamp connected between battery negative and power wire “E” with wire harness connected on EGR valve; result was test lamp did not turn on as if test lamp was connected between ground and ground.
Next I back probed with test lamp connected between battery negative and power wire “E” with wire harness disconnected from EGR valve, result was test light turned on as it should have happened but the red light lit extremely dimmed which leads me to believe this wire has lots of resistance.
Could you please help me with this?