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Matt Kesler
Matt Kesler, ASE Certified Mechanic
Category: Chevy
Satisfied Customers: 2734
Experience:  ASE Certified - 20+ Years of Experience
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03 Monte Carlo: that wont start..security light..dash..battery light

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I have an '03 Monte Carlo that won't start sometimes I think due to the Pass Lock system. I turn the key, everything in the car comes on but the security light flashes on the dash, the flash alternates with the battery light flash. Usually the car will start after waiting 30 minutes or more. What could this be?

Morgan Davis
It sounds like you have a short in the passlock system. It's failing to read the key properly sometimes and slipping into lock-out mode like it would if the car were potentially being stolen.

The only way to cure this permanently would be to have your local GM dealer service the system. They keep the software proprietary (for obvious security reasons so a random car thief can't connect to the system and steal a car easily) so they are the only ones who can help repair the system to keep it from happening again.

The only procedure for resetting the Passlock I am familiar with (to avoid the 30 minute reboot time) is to turn the key to the ignition position and leave it for 5 minutes. Then turn the key off and wait 5 more minutes. You should then be able to start the car regularly (assuming your malfunctioning Passlock module recognizes the reset procedure like it should).

All this will do is reset it temporarily though and it won't cure the problem permanently. The only way to have it permanently repaired is to have a GM Dealer service the system.
Customer: replied 9 years ago.
That didn't work. Still wouldn't start. It starts now. Same thing happened yesterday. It seems like it started after the weather warmed up. Last night and the night before were the first cool nights we have had here in Nashville.
It sounds like your passlock is malfunctioning. Unfortunately, sometimes when it malfunctions part of the problem is it failing to accept the reset procedure.

The weather could be just enough to trigger it because of the simple expansion and contraction of circuits and connections due to temperature changes.

The security light flashing almost definitely indicates passlock is the root of your problems so you may want to have a GM dealer repair department run some diagnostics. Hopefully, they can just run a hard reboot on the system and reprogram it to operate properly with no hardware replacement.
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