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2003 c5 corvette won't start

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Old Oct 23, 2025 | 07:27 PM
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Default 2003 c5 corvette won't start

Have a 2003 stick wont start had clutch switch replaced good battery try to start 13 volts gose to 0 no cranking just drove it two days ago no problem any suggestions
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Old Oct 23, 2025 | 07:46 PM
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First thing get your battery tested !!…13 volts doesn’t mean ANYTHING !!
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Old Oct 23, 2025 | 09:22 PM
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Either battery, loose ground, or bad starter.
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Old Oct 23, 2025 | 11:29 PM
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Check your battery cables, make sure they are clean and tight.
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Old Oct 24, 2025 | 01:18 PM
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Default C5 won't start

Hey thanks guys I am going to switch out the battery from another car I have that works took to auto zone they said it was good dont know if they load tested it or just seen if it had 12 volts I'll let you know how it gose and I will fill out my profile new to the site figuring it out just figured out what a thread was and how to talk thanks again
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Old Oct 25, 2025 | 09:46 AM
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Hey was going to check out my battery it's about 37 degrees figured I'd just try to start it it started shut it off started again any ideas when it wouldn't start no clicking had the neutral safty switch changed and good battery afraid to drive it and shut it off any specific spots to check for power loss if it happens again when it doesn't start it acts like the clutch isn't pushed it volts on the guage go to 0
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Old Oct 25, 2025 | 10:40 AM
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Could be the Ignition switch start contacts, it maybe the clutch safety switch needs adjustment. Without testing with a DVM it's extremely difficult to determine what the problem is. Most people describe the problem when the car doesn't crank over as a loss of power, when in reality the Ignition switch contacts turn power off to things not needed for the car to crank over and start. Have you checked the items that forum members have posted?
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Old Oct 25, 2025 | 12:01 PM
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When you have a no start condition and press the ignition key to start position , I recommend to measure the voltage level between
ground (G202 at passenger footstep behind cover (last image)) and each pin of TDR relay (C1-red, C2-Yellow,A1-Yellow/black) ,A2-Purple)
and report back
The TDR relay is located in passenger footwell above the Body control module





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Old Oct 25, 2025 | 12:34 PM
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One simple test to do when it won't crank over, shift the car into neutral, hold the key in the start position, and press and release the clutch pedal. You should hear the TDR in the passenger footwell area click on and off. This simple test will rule out the Ignition switch and clutch safety switch as the cause of the no cranking problem.
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Old Oct 25, 2025 | 11:07 PM
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Originally Posted by oelarse
When you have a no start condition and press the ignition key to start position , I recommend to measure the voltage level between
ground (G202 at passenger footstep behind cover (last image)) and each pin of TDR relay (C1-red, C2-Yellow,A1-Yellow/black) ,A2-Purple)
and report back
The TDR relay is located in passenger footwell above the Body control module




100% oelarse nailed it! As everyone else has stated, Checking the actual state of the battery and making sure that your battery cables are properly connected to the battery is first thing critical!!

The schematic provided above is absolutely required when troubleshooting this type of problem.
The THEFT DETERRENT RELAY (TDR) is the heart of the cranking/starting circuit. Obtain a volt meter and you can see if the relay is receiving the crank voltage from the ignition switch (yellow wire to chassis ground when key is in the crank/start position)
The yellow/black stripe wire is a ground wire. Its controlled/grounded by the BCM and supplies ground to the relay when all the cars security requirements are set. You can GROUND the yellow/black wire to by-pass the BCM security requirements.
The large gage RED wire is hot at all times with battery voltage from a 60-amp fuse. (fuse# 52).
The large PURPLE wire goes to the starter solenoid. When its powered, (relay contacts close) the started solenoid energizes, pulls in to power the starter and crank the engine.

If you use the colors/function of the wires, you can PROVE what is/is not happening in the circuit.

NOTE!! When you turn the ignition switch to START/CRANK, the battery voltage indicator / meter is supposed to go to ZERO! Its NORMAL.

All of that said, Its not too far to state that you may have a (BAD CONNECTION on the starter solenoid OR a BAD SOLINOID. C5 starter solenoids are very well known to go bad.
NOTE! Sometimes, If you thump the starter/solenoid with a substantial object (hammer, crescent wrench, etc.) If the starter/solenoid is bad, it sometimes allows it to crank again. I'm NOT saying you have a bad solenoid. Troubleshooting at the TDR with a voltmeter will help you figure this issue out.

I don't like telling people about the NEXT thing to try but, if you use this test,
NOTE!! CAUTION!!! You are OWN YOUR OWN AND ACCEPT any and all responsibility/safety! Make sure the transmission is in park/neutral, wheels are chocked and E Brake set! Failure to follow these cautions could cause the car to drive off on its own or inexpertly move using this test!

If you JUMP the PURPLE & RED wires together on the back of the wiring harness connector, it should cause the starter to crank. If you turn the key to the run/on position and jumper the red black wires , it will/should crank and run.
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