I've been having an intermittent no start issue in my 2001 Z06 for the last year or so. I thought I had it fixed several times but it keeps coming back eventually. The car has a new battery, starter, ignition switch, clutch safety switch and TDR. I have no codes in the DIC. The security light goes out when I insert the key and does not come on after a failed start attempt. When I insert the key, the plug coming off the cylinder lock shows the correct resistance so I don't suspect the key. I've also tried the second key with the same result. I checked the new clutch safety switch and it has continuity with the switch depressed. The red wire at the TDR shows 12v with the key off. Purple wire shows 0v when trying to crank. The yellow wire shows 0v while trying to crank. The yellow/black wire shows 245 ohms when trying to crank and open loop before cranking. I believe the BCM not properly grounding the TDR is the culprit but I'm not sure where to go from here. I have taken apart the ground plugs next to the headlight buckets and cleaned them. They looked good with no corrosion. The car has 32,000 miles on it with just bolt ons. I also took apart my original ignition switch and cleaned all the contacts per Bill Curlee's thread. I put the old ignition switch back in with the same result. This problem started a few months after I installed a double din head unit but I don't think it is related. I removed the head unit and harness along with the wire I ran to the ACC power wire in the passenger footwell and still get the intermittent start. If anyone has any suggestions or can think of something I am overlooking I would greatly appreciate any help.

Cheers

 

So yes the yellow wire should have 12v when the key is in the start/crank position and the yellow/black striped wire coming from the BCM should be ground, you might want to check the ground connection for the BCM, I don't know where that is but maybe somebody here can help.

 

Thanks for the reply, it appears my new ac delco (made in china) ignition switch was the source of my problems. It has been in the car for around 6 months. I opened it up and noticed that the center tab that moves between two contacts when you insert the key was bent off to the side. I didn't think to take a picture of it. It was black like it hadn't been making good contact. I cleaned it up and bent it back to the center. So far so good after about 10 starts. Wish I could find an American made switch but it looks like I am out of luck on that.