Won't Start and Security Light

Now my car will not start (turn the key over and nothing) from time to time. If I wait a few minutes and put the key back in the ignition it will turn over and start. My security light also comes on once in a while. My mechanic says it is pulling a 1641.
What can this be, a bad ignition switch?

I had a similar problem with a '99 lesabre.
It turned out to be the fuses under the dash,
fuse was good, but the contacts needed cleaned.
I hope this helps.

That would be the VATS (Vehicle Anti-Theft System). Fuses are a possible cause, but a more likely cause is a dirty or worn out "chip" in your key. The keys have a resistor in them that completes a circuit in the ignition to verify the correct key. The simple quick fix is usually using the eraser of a pencil to clean the chip on your key. Alternatively, you can use a q-tip and some rubbing alcohol on the key and on the ignition terminals.

If your key is after market (doesn't say GM) then it may be worth investing in a new key, or using your spare for a while to confirm the problem is not elsewhere in the system.

As an aside, I don't think the P1641 code is related.

my buick tech says its none of these answers i see listed here my car does same thing. wait 4 min only try the key the one time it will start after 4 min every time if you only try it once. it is a bad module personally i just leave early 5 min or so for everything. not enough money to fix the thing. also my car has well over 214,000 on it looking for new. had many problems with the secutiry and anti theft on this car. i say sell it and cut you losses.

If the above doesn't fix your problem and you don't care about the security chip, take an ohm-meter and measure the resistance of your key's chip. Go to radio shack and buy a resistor of the same value, then splice the resistor across the terminals inside the ignition switch. This will bypass the security chip and cure most problems.

The most common problem I've heard of with the Vats system is that with a high mileage car such as yours, tkeyes, the ignition switch has been turned so many times that the wires leading to the terminals in the ignition were stressed to the point of failure or very loose connections. Many times you can take apart the ignition switch and re-solder the terminals to fix the problem.

Inside the key lock cylinder opening are two contacts that touch the resistor in the key. Those wear from inserting and taking out keys over the years.

The two fine wires that go down the column to the connector at the base of the steering column are bent where the wheel is tilted up and down. This eventually breaks one of the fine wires in small wire. Then another breaks. This changes the resistance slightly. Eventually it's out of range (+ - 10%) for the theft deterrent module to read.

If the problems get too bad get resistors from Radio Shack and jump the two fine wires where they go into the connector at the bottom of the column. Or have someone who does it regularly installing theft alarms. They bypass the GM setup to use their own and they get the resistors in packs and replace these.

http://vats.likeabigdog.com/

if you want a video clip of what there talking about go on u tube and type in gm bypass i did a 97 bonni its pretty ez to get it fixed is over 300 the resistors fix is less than 10$ buy a resitor multi pack

Problem is fixed, it was a bad ignition switch.

jeffs2002 : The ignition switch you had replaced, did it have the VATS, Did it have the resitors on the key? Altogether how much did the replacement cost?

Glad you have the problem fixed

It ended up costing just under $300., but that included the new ignition switch, 2 keys and labor.

Problem is fixed, it was a bad ignition switch.

Do you mean ignition switch down on top of the steering column under the dash?

Or ignition lock cylinder up on top where the key goes in?

If it was the ignition lock cylinder it most likely was the contacts or the wires going down the column. A resistor bypass would have been much cheaper.

A theft alarm shop would have installed the resistor bypass for a much lower fee, if you didn't want to do it yourself.