Car computer problem

I have a 2001 Monte Carlo. It has 112,000 miles. I replaced the battery in July. I recently had the alternator replaced. At that time, my mechanic lost my key and keyfob. He replaced both. After I had the car back for about a week, the sevice vehicle soon light started coming on. Then the battery and security light would come on the “information center”. When the battery symbol flashes, the voltmeter drops to nothing. What is weird is that I do not seem to loose power, but eventually the radio locks. I can turn the radio off, then back on. I am wondering if my computer is going bad, or it needs resetting and how much it might cost.

“…the sevice vehicle soon light started coming on…”

That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.

Regarding warning lights:

  1. if the coolant temp light comes on, shut off the engine ASAP

  2. if the oil warning light comes on, shut off the engine ASAP

  3. if a FLASHING MIL/CEL comes on, shut off the engine ASAP

    ASAP means driving to the berm of the highway right now and not waiting for the next exit.

But if the MIL/CEL is not flashing, then it’s not an urgent indicator.

Thank you. I will get that done tomorrow.

OK, the guy @ AutoZone only got one one code… PO420… He said it was an O2 sensor, but that would not explain the radio locking and the security light would it?

You don’t loose power immediately because the battery will last for a little while. I doubt the loss of battery power is due to the computer though some ECUs do control the voltage regulation of the charging system. I don’t think your car is one of them. It appears the charging system is having a problem somehow and you need to have it checked out. The alternator may be intermittent.

The radio locking and the security light are unrelated problems. The CEL is only for engine emissions.

Have someone else check out the alternator. Rebuilt (or remanufactured) alternators have about an 8% failure rate right out of the box. Alternators are not designed to charge almost dead batteries. They are designed to “maintain” a battery’s output replacing the charge lost by the battery in servicing all of the electrics and electronics in a vehicle. Some places will check your alternator out free or cheap because they want you to buy a new battery and/or a new or rebuilt alternator from them. Get the alt. checked out, ask for a print-out of the test, and if it is a bad alternator, take the read-out back to the shop that sold and installed the defective alternator. He’ll see right away that the alternator was defective from the ‘git-go’. That shop should have done a check on the alternator after installation and before they put you back into your car. Have the battery’s specific gravity checked. If it’s low, ask the shop to re-charge your battery on ‘LOW’ rate while he’s replacing the alternator. Then check the battery’s specific gravity again before he puts the battery back in. If it’s a really low battery, have your battery paperwork ready so you can have a new battery prorated. You have less than 6 months on that battery. You might qualify for a free new battery depending on battery manufacturer and terms of the warranty. Be aware that most new batteries will only carry a warranty as to the original purchase date of the first battery that you had replaced in July. If you squawk a little, nicely, of course, the battery guy just might give you a full-term warranty, but you gotta be nice to them. Just a word of advice. (Don’t ever P.O. your counter person. Be nice and they’ll remember you in a fond manner.) I suspect that an intermittent alternator output is causing some of your other electrical/electronic problems. You could also consider taking the car back to your own mechanic, bat your eye lashes a little bit, BIG smile, and ask if he’ll do tests on the alternator and battery.

Thanks for the input. I will take y’alls advice. I will post when I have done so.