Hello Everyone,
I have a 2001 Lesabre Limited and the check charging system notification came on the dash. I thought it was a simple bad alternator. I replaced the alternator and the light is still on. Here's the catch... I had the alternator and battery tested at Advance auto and everything tested fine. My guage on the dash reads 12.9v running or not running but when I test at the alternator with a multimeter it reads 14.5v and the same at the battery. I thought my Instrument cluster was bad since the volt guage on it read 12.9v no matter on or off and the actual reading was 14.5v so I replaced it. The new Instrument cluster does the same thing. Can someone please help?

 

Can I suggest the following?
What is the voltage reading at the cigarette lighter ,engine off. ?
What we are looking for is where the voltage reading drops off.
The battery , I believe is located under the rear seat, correct?
There could be a corroded connection coming from the fuse/battery location up to the instrument cluster.
What is the voltage reading at the heavy gauge wire at the alternator ,engine off ? Could also be a possible ground connection.
A lot will depend on what readings you get. Let us know, thanks.

 

I would get a OBII reading and if no codes take it to some one for service. Probably cheaper than throwing parts at it like you have been. I would check all connectors to clean and tight all grounds for clean and tight also.

2001 was the first year GM did away with about 750 pounds of wireing in the LeSabre and uses a main line wire link to all computers. Body control computer, engine control computer, HAVC computer and rear lighting computer.
So there isn't a lot that can be wrong with the wireing so to speak but the computers on the other hand HUMMMMMMMMM.

Al

 

Alleyyooper brought up a good point !
Another good point is the various modules in the network are extremely sensitive to voltage fluctuations. Connections are always a good place to start.
Voltage drop testing is the way to go.