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2003 Grand Prix intermittently won't start and sometimes dies while driving

We have a 2003 Grand Prix. For the last few years it has this intermittent problem. Sometimes it just won’t start and occasionally it will die while stopped at an intersection. I did some digging online and found out what the likely culprit is, but do not know how to fix it. I already spent a lot of money for a mechanic to claim he fixed it, but didn’t.

According to online sources the security system TDM is at fault. It stops recognizing the VATS transponder in the key and thinks the car is being stolen. So, it cuts the connection to the engine. Clearly a dangerous situation if you are driving. My 17 yo daughter recently got stuck in a very busy intersection.

The temporary fix is to turn the key to the on position without turning the engine, wait 10 minutes then try starting the car. This is supposed to reset the security system. Now this is starting to not work.
Someone suggested bypassing or modulating the TDM signal by adding in a resistor. I really don’t feel equipped to do this though. Another solution is to buy a bypass module.

I am hoping someone has a simple less expensive solution.

Check the Fuel Pressure Regulator. Remove the oil cap and lift the plastic shroud covering the top of the engine. The regulator is located there on the right and its about an inch in diameter with a vacuum line running to it. Pull the vacuum line off and if there is fuel present, that’s the culprit.