2003 Buick Century security system. When the ambient temperature goes above 90 the security system is set, even with a cold engine. Below that, everything works properly.

Asked by Aug 31, 2017 at 10:31 PM about the 2003 Buick Century Sedan FWD

Question type: Maintenance & Repair

2003 Buick Century security system.  When the ambient temperature goes above 90 the security system is set, even with a cold engine.  The car will start after the 10 minute wait.  Below 90, everything works properly.  We did the full system reset, but the problem is still there.  It all seems heat related, but we don't know why.

3 Answers

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The culprit on the GM VATS system is usually the lock cylinder. Inside of the lock cylinder there's two tiny wires that contact the chip on the key when you insert the key. They tend to wear and eventually break. Sounds like when the weather is hot things expand and the wires aren't making proper contact with the chip on the key. Now here's the fun part. When you change the lock cylinder you will get a template for cutting new chipped ignition keys. You must first determine which VATS key you have. There were 15 possibilities. Once you know which key you have you can buy the correct blanks and have them cut using the template. Check the resistance value, using an ohmmeter across the chip. I have a chart that will tell you which key to get based on the resistance value. Post your resistance value and I'll let you know which key you need. HTH. - Jim

1 of 1 people found this helpful.

More details. Car in the driveway, thermometer in the car. Started the car every two hours, no problems. Temps up to 120. The last check was after dark, temp down to 90: No start. Left the key in "ON" position with security light blinking. Wait 2 - 3 minutes until light is on steady. Turn key to off, then start. Yay, it works. Same thing twice today, car temps at 100 and 90. Will bypass the ignition switch sensor with a resistor, per internet. If this confirms a bad switch we will replace it. Would it really help to have the system scanned?

Dealer scan gave us a B2958 code. I also did the resistor bypass and the car starts & runs without any security light. An AC Delco ignition lock cylinder has been ordered so we can reset it to match existing keys. I have the key resistance and VAT number, but resetting the lock is cheaper.

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