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Q: Security light flashing. No crank no start. After truck sits with battery disconnected,the truck will start and run. Is it the BCM

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My Tahoes security light is flashing and it's a no crank no start. I replaced the pass lock sensor and still didn't work. The Tahoe was sitting for about 1 month with the battery disconnected and I charged it up and turned the key over and the truck started right up. Drove it around for 4-5 hours, shutting it off and starting it over and over. Then after about an hour it did the same no crank no start with sercurity light flashing again. Got a new lock cylinder but nothing again. Do you think it is the BCM?

My car has 208000 miles.
My car has an automatic transmission.

Typically when the battery has been disconnected for an extended period and is replaced, an error code will be triggered in the ECU of the vehicle and disable the ignition system. This is done as a security feature; but tends to be a major inconvenience for car owners. The only way to resolve this issue is to have a professional mechanic complete a check engine light inspection, so they can download the stored error code, clear the code and verify that the car will start. If this is not the problem, a more in-depth inspection will need to happen.

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