C5 corvette starting problem
Melting Slicks
Joined: Sep 2008
Posts: 3,130
Likes: 799
From: Espanola New Mexico
Random no crank problems usually end up being the starter or solenoid, but jumpering the two wires at the TDR socket will help diagnose the problem to control or starter/solenoid.
Thread Starter
Heel & Toe
Joined: Jun 2020
Posts: 17
Likes: 0
From: New York
The C5 starting circuit is very simple, when you turn the key to start, the ignition switch sends 12 volts thru the clutch safety switch and then that voltage makes its way to the TDR "theft deterrent relay" located above the BCM in the passenger footwell area. The key's resistor pellet is read by the BCM thru two wires that originate in the ignition switch, if the BCM receives the correct signal then the BCM provides a ground to the negative TDR terminal. The TDR switches 12v and that wire is the heavy gauge purple wire on the TDR socket that connects to the starter solenoid switch terminal. The first thing to verify is that the TDR is being energized or clicking when you turn the key to the start position.
Melting Slicks
Joined: Aug 2013
Posts: 2,491
Likes: 315
St. Jude Donor '15-'16-'17-'18-'19-'20-'21-'22
If you jump it and there is a start, Do we eliminate the solenoid and starter as the cause of the problem. Isn't it possible though that some starter on the way out will still start sometimes? Thanks.
Racer
Joined: Sep 2019
Posts: 278
Likes: 150
From: Calgary AB
I just jumped my TDR, starter kicked over right away. So it looks like it is not the starter. So ignition or TDR is the problem on mine. When I click the key on I don't hear anything from the TDR. Not sure if it is even suppose to make a sound.
Racer
Joined: Sep 2019
Posts: 278
Likes: 150
From: Calgary AB
I might have solved the issue with mine. I took a bunch of Q-Tips and flattened the ends. I dipped them in alcohol and inserted into the ignition. The contacts inside were very black.... I did this quite a few times until the Q-Tips stopped showing black. I believe the contacts were burnt and dirty. I also cleaned the contacts on the key.
I started it a bunch without the no start issue, time will tell I guess, I am hoping it was the ignition contacts that was causing the issue.
I started it a bunch without the no start issue, time will tell I guess, I am hoping it was the ignition contacts that was causing the issue.
Melting Slicks
Joined: Sep 2008
Posts: 3,130
Likes: 799
From: Espanola New Mexico
What you cleaned was the roller contacts that press against the resistor pellet on the key. The ignition switch contacts I mentioned can not be cleaned externally, you must remove the ignition switch from the dash and do some disassembly in order to clean the contacts, or buy a new ignition switch assembly. There is an excellent sticky on this site that details how to remove the ignition switch and clean the contacts.
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Melting Slicks
Joined: Sep 2008
Posts: 3,130
Likes: 799
From: Espanola New Mexico
One last thing, you can have someone turn the key to start while you touch and hear the TDR click on, it should click on every single time you turn the key to the start position, if the TDR fails to click on every time then your problem is the ignition switch, if it clicks on every time but the car fails to start it could be your TDR or your starter solenoid.
Safety Car
Joined: Dec 2011
Posts: 4,704
Likes: 239
From: Redondo Beach CA
What you cleaned was the roller contacts that press against the resistor pellet on the key. The ignition switch contacts I mentioned can not be cleaned externally, you must remove the ignition switch from the dash and do some disassembly in order to clean the contacts, or buy a new ignition switch assembly. There is an excellent sticky on this site that details how to remove the ignition switch and clean the contacts.
Because of the age of my car, I just replaced the old worn and dirty start circuit contact mechanism for new.
nothing wrong with cleaning any electrical contacts, but my car had big miles. the last switch lasted many miles before service was needed, so I decided the best course for me was a new part, since the worn part would be needing some kind of attention in the future, and I would rather not work on cars for fun.
My car also had screwed up wiring from poor work done by someone installing a Gm style repair on the ignition lock circuit, resulting in an intermittent contact from a broken connector. Not an easy discovery on the last problem, a dedicated corvette shop fixed it. The local GM product only garage struck out hard on that issue.
Last edited by strand rider; Jun 28, 2020 at 11:22 AM.
Burning Brakes
Joined: Jul 2011
Posts: 991
Likes: 306
From: Southern Norway , Europe
If you look into post #20 I show how to verify the function of the TDR relay 
https://www.corvetteforum.com/forums...post1601237163
https://www.corvetteforum.com/forums...post1601237163
Melting Slicks
Joined: Sep 2008
Posts: 3,130
Likes: 799
From: Espanola New Mexico
The TDR will click on or energize only when the key is turned to the start/crank position, and yes you should have a second person turning the key while you verify that the TDR is being energized.
Racer
Joined: Sep 2019
Posts: 278
Likes: 150
From: Calgary AB
I had a no start so I went down in the footwell and had a second person turn the key to start. TDR energized and clicked on the no start. I had to have a mechanical inspection done and the mechanic had a no start when he was going to pull it into the shop. He was a little confused as to the dead key as well. He didn't have the time to dig into the starter solenoid but he did mention that when it does start the starter sounded strong. He is more of a import guy but he thought that is the solenoid was bad it should just not start at all or maybe even click on key stroke. It's very random on the no start, it will do it hot or cold, no rhyme or reason. So the TDR clicks every time meaning the ignition switch is sending proper power to it, so it's either the clutch switch, TDR or starter solenoid?
Last edited by BT1991; Jun 30, 2020 at 10:32 AM.
Burning Brakes
Joined: Jul 2011
Posts: 991
Likes: 306
From: Southern Norway , Europe
You should use a DVOM and check if you get battery voltage on the purple wire to the starter solonoid. The TDR relay can click, but it it may not switch voltage to the starter solonoid due to damaged contact set
Melting Slicks
Joined: Sep 2008
Posts: 3,130
Likes: 799
From: Espanola New Mexico
As previous post states, using a DVOM on the purple wire and a good ground will verify that it's either the TDR or starter solenoid, if 12 volts is on purple wire then starter solenoid is going bad, if no voltage or voltage less then battery voltage then your TDR should be replaced. And no if it was the clutch safety switch the TDR would not be clicking.