Starting problem with 2000 Impala

2000 Chev Impala, Base model.
Every 20th time or so I try to start the car (no real pattern to it), the car will not start. No engine sounds at all. On the Message Center, I see
the red battery light, then the yellow security light flashes six times, then back to the red battery light, and so on. This will go on for ten minutes, then the security light will go solid, and the car starts fine.
When I took it to the dealership, they pulled the engine codes, and I was told that I needed to replace the Body Control Module, which was messing up the Anti-Theft on the car. $500 bucks latter, the problem still exists. Now, they want to replace the key tumbler and starting module, which is another $500. Strange thing is, about a year ago, I had an ignition coil go bad. The shop replaced that, and did a full tune up, and for several months, the car started fine. Then the problem came back, and with the onset of the cold weather, seems to be happing with more frequency. When I asked my normal mechanic (not the dealership) about the relation between the tune up and the problem going away for a while, he insists there is no correlation. I'm told that there is an issue with the tumbler/ignition module and the anti-theft system.
Any ideas? I'd like to get a better handle on this before I drop another $500, which may or may not solve the problem.
Thanks,
-C. D.
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It sounds like they are chasing down an intermitant problem with the passlock security system.. I have had quite a few, and they can be a bear... I don't know about changing the bcm to start... I sure wouldn't have started there unless I had bad voltage coming out or something... Most of the ones I diag are traced down to a problem in the ignition cylinder/passlock housing, which is where they are now.... 1 or 2 I have done has been do to a wiring concern between the 2 components...a few hundrenths of a volt loss on any of the 3 wires can cause a no start condition..as to being related to a tuneup and coil, I don't see any way it can be related... oh ya, do you have a remote start??? many of these are put in poorly and cause this problem.. I won't go naming companies and such, but you get what you pay for with those...Did the dealer say this was a guess or the most common fix or something??? At my dealer we would end up eating the diag, and labor for the second time, but the customer would have to pay for the parts....Bobo

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No remote start. When I mentioned the issue to my regular mechanic, another tech, who just had completed his ASA training on starting problems, mentioned that this very issue had come up in class.
-C. D.

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