Hey everyone,

So I have spent the last week trying to figure this one out. I have read through numerous threads to potentially identify the issue (including just about every post by Bill Curlee) - so here are the details:

2003 z06, 25k miles, I have owned it for about 8 months now and just love the car. However, a few months after I bought it, the car was having the classic ignition switch issue (trouble starting from bad pellet on the key and bad ignition switch). I replaced the ignition switch, ignition cylinder and got a new key and haven't had any issues since replacing those. Since then, I have added a vararam intake and corsa extreme exhaust. Ran beautifully over the last couple of months until about a week ago. A "cold front" came through (Cold in Texas means it dropped to about 70 degrees), and the car refuses to start in the morning when I need to get to work. I immediately got online to read through threads since it sounds like plenty of people have dealt with this. What I determined from reading is that it could a bad starter, bad ground, or bad relay or fuse. As soon as I got home, I went to start the car and it fired right up without issue (turned it on and off multiple times without a problem, given it was also about 90 degrees outside). Thought it was maybe a one time deal, until I got up for work the next morning and it wouldn't start again.

When I go to start it in the morning, everything turns on as it should, gauges, lights, relay clicks, fuel pump, and there aren't any codes showing - it just won't turn over. Went ahead and replaced the starter this weekend, checked all ground wires to make sure they weren't loose or corroded, and even replaced the 'starter' (52, 60v) fuse since it was looking rough. Started right up after completing those things. Got up Monday morning for work, and of course it wouldn't start again.

One thing I am noticing is in the morning the check engine light stays on when it won't start, but blinks and goes off like normal when it does start, even though no codes come up. I am thinking about getting a code reader and plugging it in tomorrow morning when it doesn't start and also look into replacing the 'starter relay'.

To clarify a few things - the security light goes off and I also hear the clicking of the relay when the clutch is pushed in, so I doubt it has anything to do with the ignition side of things. That, and the fact that pretty much everything having to do with the ignition is less than a couple of months old.

So, at this point I am pretty stumped and wanted to see if anyone else had any additional advise. Thanks!

 

Just for giggles, check the ground strap on the back of the passenger side head. See if its loose.

 

Thanks. I will check it out right after work and update you.

 

Well,,,,,,,,,,,,,,,,,,, You must have THIS schematic to troubleshoot that issue. (SEE BELOW)

The HEART of the system is the THEFT DETERRENT RELAY. You can start troubleshooting there and tell EXACTLY what is and isn't happening when the starter will not engage.

The TDR Relay is nothing more than High Current SWITCH

you complete all the interlocks to apply 12 VDC Low Current power to the RELAY COIL which closes the 12 VDC HIGH CURRENT switch to energize the starter solenoid which is an even BIGGER high current switch.

The YELLOW/BLACK STRIPE on (A1) wire completes the circuit to ground (when all of the vehicle security requirements are satisfied).

When the starter will not run, do you have 12VDC on the PURPLE WIRE?

When you press in the clutch, turn the key to START do you have 12VDC on (C2)

IF,,,,,,,, all of the voltages and conditions are correct at the TDR, you have to look at the battery circuit to the starter. EVERY CONNECTION from the battery to the starter/solenoid MUST be clean and tight.

 

Very interesting for sure. you've been checking codes the whole time I assume? Tried another battery? I'm far from a C5 electrical expert, I'll let those guys give you some ideas. But a wonky battery is always a possibility. Terminal connections on tight? Corrosion free?

 

I have been checking codes everytime, whether it turns on or not. Even though the battery isn't even a year old, I may take the battery up to get load tested and checked out while I double check my grounds. I double checked the terminals, they were tight with very lite corrosion of which I cleaned up anyways.
It would almost be more helpful if the issue wasn't intermittent, because regardless of what's been done, it seems to always start up in the evening time. So I have to wait until the morning time to see if the issue is resolved. PITA.

 

Bill, first off thank you for contributing. You have indirectly helped in quite a few projects to the point that if I am having trouble figuring something out my girlfriend will say, "Get on the forum and see what Bill has to say". lol I will take the schematic and look at the areas you have mentioned, starting with the TDR.

I will be sure to keep you posted on what I am able to determine.

 

**Update**

The ground strap was tight and clean.

 

Check the two positive cables under the fuse cover in the engine compartment (next to the battery).Make sure the nut is tight that holds them down.

 

Will try that after work today. Thanks!

 

***Update***

Getting a DMM from my brother today so I can check the volts at the relay. May just replace the relay since it's fairly inexpensive.

Last night I went ahead and inspected the TDR and even the clutch switch. Both were clean and visually fine. My girlfriend thought it maybe a good idea to put my car in the garage over night since it stays about 10 degrees warmer, and the issue has been when I park it outside and it drops to the mid to high 60's at night. Sure enough, I woke up this morning, went to start it and it started right up without hesitation. Ended up taking it to work and drove just fine. It's just so weird that the slight change in temperature determines if the car will start or not..

 

***Update***

Another cold front came through, which means the vette didn't want to start. The amps on the battery were low, so I tried a different battery. Still didn't change anything..
I did figure out that the ignition switch is receiving current, but there isn't any current leaving the switch. Even though the ignition switch is only a few months old, I am going to replace it. Will update once this new project is complete.

 

VOLTAGE VS CURRENT

You keep saying current when I think you are measuring VOLTAGE. When you measure CURRENT, the meter MUST be set up to read current and MUST be in SERIES with the load. Current is measured in AMPS (A)/Milliamps (ma).

You should be able to crank your car when its 30 below outside. I fully believe that you are experiencing the commonly known C5/C6 Starter Solenoid failure.

The starter solenoids on our starters are WELL KNOWN to fail. When they fail they do exactly what you are experiencing.

The NEXT TIME it fails to crank,,, Have your wife sit in the drivers seat and HOLD the key to the CRANK position (clutch fully depressed), just like she is TRYING TO start the engine.
You use a wood dowel, long metal rod, broom stick ect... To THUMP the starter.

If it comes to live,,,,, YOU HAVE THE CULPRIT!

If you hold the key to CRANK and bump the clutch peddle on and off the safety on the floor/firewall, each time you press and release that switch, you SHOULD be able to hear the TDR Realy "CLICK" (meaning that all the low voltage/low current circuits are working properly to make the TDR function).

When the TDR is energized, you must see full battery voltage on the TDR (PURPLE WIRE).

Bill

 

Unclip the TDR and leave it hanging for easy access. Next time it does this, remove the relay and short between the red and purple wires in the socket with a piece of wire. If the starter solenoid is at fault, it won’t turn over.

 

remove the relay and short between the red and purple wires in the socket with a piece of wire.



YES that will work and work well BUT,,,,,,,,,,,,,

WARNING!!!

YOU MUST MAKE SURE THAT THE CAR IS OUT OF GEAR!!!!!!

If yoii dont it will MOVE when the starter turns over the engine. IF, you have the key in RUN and if it starts,,

BYE BYE CAR!!

Bill

 

Ha! Very true. Good point.

 

I have this same issue.
It is not weather related.
No fix for me except I pray for the car to start when this happens and then it starts.
I really sit there and pray. For the day and people then ask for the car to crank.
I have read all the Bill Curlee posts.
The only trick I have not tried is the broom stick to bump the starter. I just read that in his above post.
I have cleaned contacts in the tumbler.
I have bought a new key. I only had one key any how so now I have an extra. GM Factory direct cut.
Grounds clean and tight.
Inspected starter and connections.

This is my daily driver so I experience it often. Twice a month or more.
I have been dealing with this for 5 years now.
2003 auto.

 

There is a ground stud with a single wire on the left rear of the frame behind the left rear wheel. If this ground is loose or corroded the car will not start. Check it out.
Shirl Dickey

 

I shall do that. I do believe I have checked all of the grounds from the BC write up but I need to do a job back there any how so I will not hurt to check it again.

i know I have removed all of the bus grounds and made them single grounds.

 

Sorry, Bill. Electrical definitely isn't my forte - in Layman's terms, there was power getting to the ignition switch, but nothing going out. It was indeed a faulty ignition switch.