When I go to start my truck it cranks for a few seconds and my battery light comes on in my dash. I have two new batteries and my scan gage never goes down below 47v for my ficm. Sooo if it's not the ficm or batteries then what could it be? Or am I just worrying about nothing

 

If the light is on while cranking, I wouldn't worry about that, I think mine does the same. If it stays on after the engine starts the you may have a problem.

 

The battery light is for the alternator, not the batteries. It's telling you there not getting a good charge...

 

Exactly, and they won't get a charge at the low RPM during cranking. As soon as the engine starts and runs at normal idle RPM or higher, it should charge the batteries fine and the light should be off.

 

I would also say that the PCM would need to command something as well. With glow plugs still running up to 120 seconds after the motor starts, they eat a lot of amperage. Withing a couple minutes, you should see 13.5v or more from the alternator.

 

Okay thanks guys