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Kenny, ASE Certified Technician
Category: Chevy
Satisfied Customers: 227
Experience:  Providing 16 years of experience with certifications in engine performance, electrical and brakes
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2003 Chevy Impala: it wont start, the security light..fuse box

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We have a 2003 Chevy Impala that always starts in the morning. Later in the day it has problems starting at all. When it won't start, the security light comes on, then the battery light comes on and we hear a clicking noise coming from the middle of the dash and the right side of the dash fuse box. If it does start up, the security light flashes alternating with the battery light. Plus, the interior and exterior lights flash too. It's very strange. I have read online that it's a "passlock" problem, so we turn the key to ON and let it sit for 20 minutes, turn it off for 2 minutes and sometimes it will start. Sometimes we try disconnecting the battery for a few minutes. But, usually we have to let it sit still overnight until it will always start in the morning. We're going crazy with this problem, so do any of you expert GM mechanics know what we can do for this? I would be happy to give a donation if you can come up with a definite solution. Thanks in advance.
Hi my name is XXXXX XXXXX I will be glad to help you. Do you know what trouble code is setting the security light?
Customer: replied 7 years ago.
No, I have no idea what the trouble code might be. I suppose that should be our next step. The last time I took it to AutoZone for the check engine light being on, the trouble code said it was the oxygen sensor. That problem will have to wait until we get this intermittent start problem solved.

Your security light is on for one are two reasons. You should check your wire terminals in the connectors at your body control module which is mounted under the dash on the drivers side. You should unplug the three connectors at the body control module and inspect the terminals in the connector to see if they may be open more than they should be. You can do this by comparing all the terminals together and be sure they all look the same. If you find no problem with the terminals is the body control module connectors then the next step is to replace the ignition switch. If the terminals are good then replacing the ignition switch will fix your security problem. You installed a passlock bypass kit to bypass your passlock sensor which is located on your ignition lock cylinder. The problem is in your ignition switch. If you follow this procedure you will fix your security problem. I am glad I was able to help you today.

Customer: replied 7 years ago.
OK Kenny, I have a couple of more questions before we wrap this up tonight.

1.) I have been up under the dash and I have removed the big metal plate under the steering wheel. (and then put it all back of course) I had read online that I needed to solder the 3 little wires onto the ignition lock cylinder to solve this intermittent start/passlock problem. So my question is: What does the BCM thing look like and what does it say on it so I can recognize it? Then, if the terminals are bad, what can I do about it? Clean them? Pinch them tighter with plyers or what should I do about it?

2.) As for the ignition switch, I found one online. Is this what you mean at the following link? I mistakenly thought the ignition switch and the ignition lock cylinder were the same thing. Are they connected together or separate?

If so, how involved is replacing it? Where does it go? On the starter? Under the dash? I've worked on my cars for 35 years, but I've never had to do one of these. I need a little more help so I can understand this.
You should not have to solder any wires on the ignition lock cylinder. The ignition lock cylinder is the passkey sensor and it slides inside the ignition switch. You will have to remove the ignition lock cylinder to replace the ignition switch. You should remove the instrument cluster, radio, and hvac control head and then you will see the ignition switch that the ignition lock cylinder fits inside. The BCM is a square black module mounted under the dash on the drivers side that has three connectors going to it. If you may find some open terminals in the bcm connectors you can try to close them some so they can fit tighter. If you can not then they will have to be replaced.
Customer: replied 7 years ago.
The 3 wires I soldered to the three pins were on the side of the ignition switch because the little plastic connector was loosely fitting. I got to it by removing the big dash board plastic cover and then I got to it from under the dash. I had it out and in my hand with the thick ignition wire still attached. So my last questions are:

1.) How hard is it or what is the procedure to get the ignition lock cylinder out of the ignition switch? Do I need a special tool?

2.) How hard is it or what is the procedure to get the big wire out of the ignition switch when replacing it? I can connect the same wire to the new ignition switch relatively easily?

3.) I assume that I can put the same ignition lock cylinder in the new ignition switch?

That should be it for my questions.
When the ignition switch bolts are removed from the dash where you can move the ignition switch with your hand you can then put the ignition key inside and turn the ignition lock cylinder like you are going to start the car. You should place the shifter into gear so the engine does not start. With the key turned you can use a small screw driver to press a metal tab on the side of the ignition switch and then pull the lock cylinder out. Then remove the cable and electrical connectors and replace the switch. Then reinstall the same way and yes you can use the same ignition lock cylinder.
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