Electrical problem: battery light on, power draining while driving

I have a 2000 Toyota Tacoma with 285,000 miles on it. There is something that is draining my battery while I am driving for an extended period of time. Ultimately, the car shuts off. My first thought was alternator, but I removed it and had it checked twice. It came back OK. Then I took it to the dealership to have their service department look at it, and they couldn’t diagnose it either. Instead of paying them to check the wiring one by one, I am going to pick it up and see if I can’t find the problem myself. I haven’t been able to find a thread about this problem online, but I’m sure I can’t be the only one. So if anyone has encountered this issue or something similar, I would really appreciate hearing from you. Thanks.

 

Have you had the alternator checked while on the truck? Check all your fuses really good.

 

Start your truck and while in idle remove the negative ground from the battery terminal.. if the engine shuts down, thats indicate your alternator is bad... if stays running in idle then your battery need replacement.. good luck

... Or https://youtu.be/AcPmFP5R4as

 

***Back in the old days you could remove the negative cable with the vehicle running prior to computer controlled vehicles now that can cause damage $$

Most likely to old for them to plug into the high end computer

Time to break out the Multimeter.

Is the charge light on??

Once the voltage in the system the drops to low the ECM shuts down to protect itself

The truck starts fine once the battery is charged up again??

Start at the battery terminals and check all the connections

 

Thanks all for the input. Wanted to update the thread as I seem to have solved the problem, and my findings could come in handy for someone else . . .

After checking all wiring and fuses I could find and still not making any progress, I decided to get a second opinion from a Japanese auto specialist. In addition, I called beforehand and described the problem, then ran the truck around town until the battery light came back on and the power drain was occurring. I then pulled up to his shop, left the truck running, and got him to test the voltage coming from the battery. Sure enough, it was below the minimum (don't remember the exact reading). According to this mechanic, sometimes an alternator that is on the verge of failing will appear fine when the vehicle is cold. This would explain why, after being parked at the dealership for 2 days, the Toyota techs weren't able to find an issue. It isn't until the engine warms that the alternator failure occurs.

At any rate, I replaced the alternator last night and drove the truck to work this morning. So far, so good!

 

Yeah, I've had my alternator checked and come back "ok" before too.

You know what fixed my problem? New alternator...