Hello everyone, I’m having an intermittent no-start issue with my C5 and could use some guidance.

When I turn the key, all the electronics power on, but nothing else happens; there's no click and no crank. Occasionally, it will give a very quick crank, but most of the time it’s completely silent. If I leave the car alone for a bit and come back later, it will often start normally. The battery, alternator, and ignition switch have all been recently replaced and tested good.

I took the car to a shop, and this was their diagnosis:
"Duplicated intermittent starting issue. Checked for voltage at the solenoid and found that when the vehicle would not start, voltage was not present at the starter solenoid wire. Traced wiring back to the theft deterrent relay. Voltage was present going in, but it was intermittent when going to the starter solenoid. The relay is faulty and needs to be replaced."

Based on this, I replaced the theft deterrent relay (see attached photos for reference), but the issue is still happening.

At this point, I’m trying to figure out the next step. I’ve considered replacing the starter/solenoid, but if voltage isn’t consistently reaching the solenoid, that doesn’t seem like it would solve the root issue. Since the relay has already been replaced, what else could be preventing voltage from reaching the starter solenoid?

Any insight or suggestions would be greatly appreciated.

Theft Deterrent Relay (Replaced) (Passenger Side Footwell)

 

Inspect the TDR relay socket, it may have corrosion on the female contacts, sometimes water intrusion occurs underneath the dash.

 

Thanks for your reply, and that makes sense. Do you know how someone would go about testing and fixing that? I just got a multimeter, but I'm new to using it.

Additionally, I had another thought: the relay I removed was four-pronged. If I replaced it with a 5-prong, would that cause an issue?

 

If you never used a DMM before take your car to an auto electric shop...the Forum is not the place to learn !!

 

Hello775, you must first determine that the TDR is clicking on each and every time you turn the key to the start position, have someone try to start the car while you position yourself by the TDR. With your meter connected to a good ground and the other lead inserted into the purple wire socket at the TDR socket you should see 12v. Let me know what you find.