Trouble when cold starting

Good day everyone, I am new to these forums. I just bought my self a 2002 GMC Sierra 2500HD. It is actually a really nice truck. It looks like the person who had it before me had a bit of money. It has twin turbo's, diesel, Allison automatic, 4" exhaust, pillar mounted dual boost gauges, tow/haul package, SLT, sliding tunnel cover, secondary battery was moved to the box, K&N filter.

Anyways my question is about cold starting. When I went out this morning to start the truck, I waited for the glow plug light to go out and then started the truck. Only problem is it reset the stereo. The guy installed a Kenwood CD/MP3 player and this is only time it has ever done it. I am going to see if it does it again tomorrow. If it does what does it mean? Does it mean I need new batteries or alternator?

I have never owned a diesel before so I am just wondering. It only has 165,000 KM's on it. I paid $26,000 for it. I know it is probably bit high, but it was the best one I could find. All of your help is greatly appreciated .

BUMP!!!!!

Well I now have a new problem with the truck. It won't start now. I have no lights on the instrument cluster and the gauges don't move. It will start just until you release the key and then it dies. I do have power though as the headlights work and the radio comes on.

What happened is I was driving to the store and the check engine light came on. When I got to the store I checked everything over and it was fine. Started it up and drove home and the engine light was still on. So I took and checked all the fuses and they were all fine. Then when I went to go to work it would not start. I took and bought a code reader and it comes up with one code. P1643 and the book says "Fuel pump PWM Control circuit (except 5.7L VINs P & 5).

All of your help is greatly appricated!

[maxwedge]

Check for power in and out of the ign switch when in the run position, or a main fuse issue.

So today me and my friend took and put the ignition to run and were checking every single fuse we could find. It turns out the problem was a loose fuse.

[maxwedge]

Good work, these moden trucks and vehicles can be difficult to diagnose, I would get a shop manual for this and any info on the add-ons.