It died all of a sudden, now it starts and runs for a cou...

It died all of a sudden, now it starts and runs for a couple seconds, then dies. Mechanic's Assistant: Will the headlights turn on? Is the battery fully charged? After it died the first time, the headlights stayed on cons...

It died all of a sudden, now it starts and runs for a couple seconds, then dies. Mechanic's Assistant: Will the headlights turn on? Is the battery fully charged? After it died the first time, the headlights stayed on constantly. I couldnt turn them off with the switch, i had to pulp the headlight relay. To turn off the parking lights, i had to pull the tbc fuse. All the gauges except the battery voltage meter died also. This all happened an hour after i jumpstarted the pickup. I put a new battery in, but nothing changed. Its a 2001 silverado 2500hd with a 6.0, 285,000 miles. Mechanic's Assistant: Are you fixing your Relay yourself? What have you tried so far? I just pulled the relay to get the headlights to turn off. I swapped with a couple other relays, but it made no difference. Mechanic's Assistant: Anything else you want the Mechanic to know before I connect you? Ive pulled the 3 harnesses going into the bcm, there was slight corrosion on the one furthest to the right. I cleaned it up, but that didnt change anything. Ive checked all fuses, both fuse blocks.