I finally got this car in the garage for a good look. I've very closely inspected the wiring and there is no corosion or damaged wires. I buzzed all of the Injector harness wires with a multi meter and all are good conductively. I also bench tested the coils through the injector harness with a bench power supply powering with 12 Volys, but triggering with 5 Volts. One coil does seem weak, but I was loosing the entire bank. I doubt one bad coil could take down the whole bank and it does fire, just much weaker than the other coils. So I'm certian the injector harness is good and 3 coils have really good spark. Next I need to test the PCM side. The harness appears OK and according to the wiring diagram the Left & right bank share the same ground, so it shoulden't be a bad ground. I do see on the wiring diagram there are seperate 5 volt supplies for the left and right bank so, I'm thinking a bad PCM. I'm going to keep testing before I order one. I have tested the PCM side for good grounds and good 12v, but I havent had a chance to put the scope on it to look at the 5 volt signal wires.
I'm new to the LS style engine, Am I missing somethig? Can you/How do you test the resistance of these 4 wire coils?
I do need to replace at least 1 coil, go OEM AC Delco? or are there any good aftermarket coils?
All of the coils look origional and the car is 14 years old with 190K miles on it. Should they ALL be replaced? I am planning on keepin this Tahoe for a long time. I've been through this before on the Ford 4.6 COP coils and it seems they all start failing shortly after the first one fails, so you should just replace them all at once if you care about the car. Not sure if it's the same with this style coil.
Thanks!