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.

Automotive Expert
**Bradley Jordan** **Nissan, Subaru, and Infiniti Master Technician** **ASE Master Tech All Makes** **Let me take a moment to review your request.** **_You may be prompted for a phone call, this is optional as the request is automatic._** Have you checked the battery voltage, if it is below 12 volts, the bcm can hang up the lights because of the low voltage to the bcm. Also if it is not charging the truck will start and die.

I checked the battery, it is good.
Automotive Expert
Since you replaced the battery check it for trouble codes in the [engine](/topics-engine-chevy/) and BCM.

With a diagnostic tool, I'm assuming?
Automotive Expert
yes, that will narrow down the area of the failure, do you have a scan tool? this is available for I phone and android and turns your phone into a full system scan tool. It is available on Amazon for 61 bucks just follow the link below,\_1\_3\_sspa?crid=2AX2D4EC2B4IZ&dchild=1&keywords=autel+scanner&qid=1612551701&sprefix=autel%2Caps%2C207&sr=8-3-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzQzdOUUVZVjVWSTc4JmVuY3J5cHRlZElkPUEwNTIwNjkwMk1XMUZGWVVWSlhEQSZlbmNyeXB0ZWRBZElkPUEwODI2NDk5MUIzUEhCRzk0Q0tPSiZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

I'm scanning for codes right now
Automotive Expert
A voltage spike during the jump start could have caused a problem in any of the systems. ok

Scan tool won't read, it just says link error
Automotive Expert
Start by checking fuses, you may one or more blown fuses.

This all happened an hour after i jumpstarted it. It ran fine when I pulled it into the shop, just died all of a sudden. I've tried resetting the passlock system, unhooked the battery for a couple hours, double checked all fuses.All fuses check good,
Automotive Expert
try reading the codes with the bcm and pcm unplugged one at a time, a problem with a control unit can lock the scan tool out.

Automotive Expert
look at the 2 attached wiring diagram the DLC goes thru the driver information center.

Since I have nothing working on the instrument cluster, should I trace the dark green and white wire first?
Automotive Expert
I would

Should I have power on the dark green/white wire in the harness that plugs into the instrument panel?
Automotive Expert
no that is the veh speed sensor signal
Automotive Expert
here is a clearer diagram.

Ok, that's better. Where should I look first? Headlights constantly on, no gauges on the instrument panel, pickup not starting.... What relates to all three of those?
Automotive Expert
start by verifying power on the 3 circuits to the cluster. I will get you the lighting diagram
Automotive Expert
The headlight switch energizes the headlamp relay which goes thru the headlamps to the bcm.
Automotive Expert
The low beams bypass the bcm, but a problem in the bcm could leave the high beams on. also the bcm could make the headlamp relay close with the switch off. both low and high are power by the headlamp relay.

I disconnected the headlight switch, lights still stayed on.Does this indicate a short somewhere in the circuit, or could the BCM be faulty, signaling the relay to be closed at all times?
Automotive Expert
if you pull the headlamp relay they should go out because they have no power in the circuit if they stay on you have a short in the fuse box, if they go out most likely a bcm issue.

They go out when I pull the relay
Automotive Expert
check the white wire to the relay from the bcm, it should not have voltage in the off position. if you have voltage it is in the bcm if not a bad relay.

I've tried swapping out relays, so I don't think the relay is bad, but I'll check for voltage.
Automotive Expert
Automotive Expert
my wife just got home, we are going to run some errands, leave a question if you have one and I will answer as soon as we get back.
Automotive Expert
**If you need more help, just follow up with your question and I can give you more information.** **it was my pleasure to help you today, exceptional service is my goal and I hope I provided** **Exceptional service for you today. Good luck with your repairs and have a wonderful day** **Thankyou** **Bradley**

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