I followed these instructions:

"Originally Posted by jondoe28 View Post
Had this done a couple of weeks ago. Hasn't acted up once, security hasn't come on at
all either. Hired our tractor mechanic to do it. Said 2 contacts were burnt on key switch.
Used sand paper to clean them, and good to go. Cut and pasted from another site:



I just fixed my 2002 impala security light issue. It cost me 2 hours, no money. Here is how the system works. The passlock sensor and the ignition switch are in series. When you turn your key you generate a low current read by the body control module. If the current generated is out of range the BCM won't recognize the signal and your car won't start for 10 min. There could be different reasons why the signal is out of range. On most of the cases the ignition switch contacts are burned out, and this will cause a voltage drop on the contact so the signal getting to the BCM is going to be lower than usual so it will be out of range. Take your ignition switch out (if you don't know how send me your e-mail (believe me I'm not looking for e-mail addresses I just need to scan the instructions, since I have them only printed out) and I'll send you detailed instructions for free. Once the switch is out remove the cover on the back of the switch (it is clipped on, all you need is a flat head screwdriver). Once the cover is removed you should see 5 fairly big electric contacts. I bet at least one or two are burned out. Clean them with fine sand paper until their surface is clean and flat and make sure the steel springs pressing the contacts together are tight and are pushing the contacts firmly. If not, using pliers bend them to get good contacts. Reinstall the switch and your car should start every time. If the contacts are really bad you might have to change the ignition switch.
I know dealers want to change every part on the car so please do not let them change the passlock sensor. The passlock sensor is a hall sensor and there is no reason for the sensor to go bad."

After I took everything apart, and this is what the ignition switch contacts look like. They look pretty good to me.

So then what should I check next?

I have been having the intermittent Security light coming on and the car not starting.

Thanks

 

What model is t? Is this the ignition switch block?

 

Yes, that is the back of the ignition switch. 2002 Impala. I forgot to mention, the key can fall out of the ignition switch, while the car is running. The keys are quite old and worn down. Could that be the issue?

 

Doe's the security light flash with a key in the ignition?

 

The problem is intermittent. At first once or twice a month. Then three weeks ago it happened just a week apart. The security light comes on solid, not flashing and the car won't start. The second to last time, after trying to jumpstart (even though the battery was fine) about 10 minutes later, after trying over 12 times to start, it finally started. The last time it happened, solid security light, wouldn't start even after 20 minutes. When tow truck driver came, it started in Neutral. After leaving it at dealer for 2 weeks, they couldn't replicate the issue.

Just before I took it apart, the security light was flashing with the key in the ignition. it alternated between "security" and the battery symbol.

 

Should I go ahead and change the ignition lock cylinder? and maybe the ignition switch if that doesn't work?

 

I would recommend doing that.

 

May i have a copy too? Milehijos@gmail.com

 

Hi mobile installer could you please email me the diagram of how to bypass the Passlock security system in a 2004 S-10 pickup LS my email is kkonski13@gmail.com

 

I was about to go ahead and order a replacement ignition lock cylinder and switch, when I came across this quote in the previous thread - would you agree that replacing the lock cylinder and switch is not the way to go?:
Originally Posted by mobileinstaller View Post
ok first off changing the ignition switch and tumblers will do absolutely nothing sorry if you have already done this. there are three main components to the passlock II system the passlock sensor, the BCM, and the Ecm and of course the wiring in between. Odds are if this keeps happening and there is no other problems such as door locks freaking out trunk release just goin off then it's not the bcm if you do the relearn feature and it works the it is also not the Ecm. so you are left with the 3 wires that run from the bcm to the passlock sensor.odds are the passlock sensor is bad. now there are two solutions either go to the dealer and have the sensor replaced or bypass the system for good. any respectable mobile electonics installer should be able to do this no problem it takes me about 20 mins and i personally charge 40 dollars to do so hope this helps also if you are mechanically inclined in electronics i can send a diagram on how to bypass it yourself hope this all helps