2003 c5 corvette won't start
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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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.















