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Cadillac Repair/2000 Cadillac


I changed the battery now it won't start


You have a so called anti theft system known as PK III. It is equipped with a chip in the key that is programmed to the computer. The most common thing that happens with these anti owner systems is that when the battery is disconnected over a minutes time is that the PK III  transponder memory is lost from the computer and will not recognize the key.
There are two things that done to be reprogrammed, which also require new key blanks.
You can have the car towed to a dealer and get ripped off for an extraordinary high dollar amount for reprogramming and Kay's.

Option 2 is to call a locksmith to come to the car to do the same thing the dealer would for half the price.

Most people think the dealer is the place to get replacement keys not realizing the factory has nothing to do with the production of keys and locks. This was all subcontracted to a Milwaukee company for GM Ford, Chrysler.
So, the locksmith gets keys and locks from the same place the dealer does. The dealer is a high priced middleman.

This is all with the assumption that this is the common problem.
Why did you change the battery? Were you having some other issue that you thought a new battery would fix?
It's very common for people to change a battery and an alternator because the engine did not crank, when chances of needing both are very slim. In some cases,the alternator and battery were not the problem, turning out to be a starter.
If the battery was replaced because of maintenance, or it was bad, then your problem is most likely the memory loss for the ignition key.

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Rob Painter


Alarm system questions cannot be answered on this forum. These systems are not what I can answer. Without being physically at the vehicle and not knowing what kind of electrical service has been done on the vehicle, there is no possible way to give an accurate answer over the internet. My expertise is in Ignition/key based anti-theft systems. These issues include GM VATS (resistor chip in key blade) PASSLOCK (MRD)-ignition lock rotation based, no special ignition key and the PKIII Transponder (computer chip in key) systems. These systems are not alarm based and are integral with the starting of the engine. This is why I cannot diagnose alarm problems without physically looking at the vehicle: Alarm systems are a completely different annimal than ignition key/lock based anti-theft system. Many alarm questions come from vehicles 10 years old, and since older, many hands that had been involved over the years.I am an expert in all GM factory (ignition/key based)systems. Alarm system questions pose to many situations beyond my knowledge as to what has been done to the vehicle over the years. Some guy may have actually wired the stereo into the alarm system. Who knows? Over my past 30 years in vehicle wiring repair, I have seen unbelievable wiring disaters done by guys that consider themselves "mechanics." I have seen stereos and alarms intalled using surgical tape. I have seen modules burn up, un-fused circuits, wiring jambed between the doors and even lamp cord used for a starter kill. To answer alarm questions over the internet without examining the vehicle is like asking; What does it take to remove a dent?


Education/Credentials-ASE certified. 11 years with a GM dealer and 17 years with a repair facility dealing with only the repair of theft recovered vehicles.

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