Electrical Problem

raptorman · January 31, 2010

Got a strange electrical issue I'd like some guidance on my 2000 Sierra 1500 5.3l....Yesterday while driving to work, I had a very brief power interruption (all power clicked off and maybe a half second later kicked back on). When I parked my truck at work and shut it off, I lost all electrical power. The doors locks would not even operate. When I restarted it, it turned over, fired, then died. It did that about 4 times until I just mashed the pedal down and crank it. It finally started and as long as I kept the RPMs at about 1k it would stay running. If I let off the pedal it would idle out and die. As I was driving home after work, my gauges were tuning on and off and my dash lights were coming on and off. The engine stayed running but the gauges and dash lights were going hay wire. I thought it might be an alternator due to the fact I had to keep 1k RMPs to keep it running. So on my way home, I bought a new one and went home and changed it. This seemed to fix the problem for about an hour. I thought I had it fixed until I noticed the same brief power interruption as I was pulling out of a parking lot. Again I started experiencing all the previous symptoms. Any idea what it could be????? I would rather fix it myself than take it into a shop. Any pointers in the right deirection would be great

AThomas7782 · January 31, 2010

Have you tried a different battery?

rmck490 · January 31, 2010

Got a strange electrical issue I'd like some guidance on my 2000 Sierra 1500 5.3l....Yesterday while driving to work, I had a very brief power interruption (all power clicked off and maybe a half second later kicked back on). When I parked my truck at work and shut it off, I lost all electrical power. The doors locks would not even operate. When I restarted it, it turned over, fired, then died. It did that about 4 times until I just mashed the pedal down and crank it. It finally started and as long as I kept the RPMs at about 1k it would stay running. If I let off the pedal it would idle out and die. As I was driving home after work, my gauges were tuning on and off and my dash lights were coming on and off. The engine stayed running but the gauges and dash lights were going hay wire. I thought it might be an alternator due to the fact I had to keep 1k RMPs to keep it running. So on my way home, I bought a new one and went home and changed it. This seemed to fix the problem for about an hour. I thought I had it fixed until I noticed the same brief power interruption as I was pulling out of a parking lot. Again I started experiencing all the previous symptoms. Any idea what it could be????? I would rather fix it myself than take it into a shop. Any pointers in the right deirection would be great

It may have something to do with the battery. It's either bad or a bad connection. Check you grounding point first, clean that, and clean the battery terminals. See what happens after doing that.

raptorman · January 31, 2010

Got a strange electrical issue I'd like some guidance on my 2000 Sierra 1500 5.3l....Yesterday while driving to work, I had a very brief power interruption (all power clicked off and maybe a half second later kicked back on). When I parked my truck at work and shut it off, I lost all electrical power. The doors locks would not even operate. When I restarted it, it turned over, fired, then died. It did that about 4 times until I just mashed the pedal down and crank it. It finally started and as long as I kept the RPMs at about 1k it would stay running. If I let off the pedal it would idle out and die. As I was driving home after work, my gauges were tuning on and off and my dash lights were coming on and off. The engine stayed running but the gauges and dash lights were going hay wire. I thought it might be an alternator due to the fact I had to keep 1k RMPs to keep it running. So on my way home, I bought a new one and went home and changed it. This seemed to fix the problem for about an hour. I thought I had it fixed until I noticed the same brief power interruption as I was pulling out of a parking lot. Again I started experiencing all the previous symptoms. Any idea what it could be????? I would rather fix it myself than take it into a shop. Any pointers in the right deirection would be great

It may have something to do with the battery. It's either bad or a bad connection. Check you grounding point first, clean that, and clean the battery terminals. See what happens after doing that.

I will do that when it gets back from the body shop. Where is the ground on this year GMC? I don't know how it could be a battery though. Why would my gagues turn on and off and all the dash lights go haywire? It seems like a computer problem to me but I will check the connections and battery when I get it back.

rmck490 · January 31, 2010

Got a strange electrical issue I'd like some guidance on my 2000 Sierra 1500 5.3l....Yesterday while driving to work, I had a very brief power interruption (all power clicked off and maybe a half second later kicked back on). When I parked my truck at work and shut it off, I lost all electrical power. The doors locks would not even operate. When I restarted it, it turned over, fired, then died. It did that about 4 times until I just mashed the pedal down and crank it. It finally started and as long as I kept the RPMs at about 1k it would stay running. If I let off the pedal it would idle out and die. As I was driving home after work, my gauges were tuning on and off and my dash lights were coming on and off. The engine stayed running but the gauges and dash lights were going hay wire. I thought it might be an alternator due to the fact I had to keep 1k RMPs to keep it running. So on my way home, I bought a new one and went home and changed it. This seemed to fix the problem for about an hour. I thought I had it fixed until I noticed the same brief power interruption as I was pulling out of a parking lot. Again I started experiencing all the previous symptoms. Any idea what it could be????? I would rather fix it myself than take it into a shop. Any pointers in the right deirection would be great

It may have something to do with the battery. It's either bad or a bad connection. Check you grounding point first, clean that, and clean the battery terminals. See what happens after doing that.

I will do that when it gets back from the body shop. Where is the ground on this year GMC? I don't know how it could be a battery though. Why would my gagues turn on and off and all the dash lights go haywire? It seems like a computer problem to me but I will check the connections and battery when I get it back.

Yes, you may have a computer problem but let's do the basic no cost checks first so you don't expend a ton of $ on it just yet. This may not cost you more than a new battery.

For my Silverado, the attached diagram shows the grounding point for the battery on left side of the engine block.

minibike132 · January 31, 2010

Battery and cable checks first. Igniton switch is my guess if those check out.

Are there any codes?

raptorman · January 31, 2010

I didn't have any time to get any diagnostics done on it since I had to take it into the body shop the same day so I don't know if there are any codes and what they are. How much is a new computer? Is this something I can do myself if it ends up being a new comp? I'm pretty savy in wiring and wire repair since I am an aircraft electrician.

minibike132 · January 31, 2010

Do not put a new computer in it unless there is some diagnostic to support it. With the issues you are explaining you would be wasting your money. If there were U--- codes that inidcated some sort of communication issue there could be a controller interrupting communication but with the symptoms that controller would not be the PCM, it would be one of the others.

raptorman · February 1, 2010

You think it would be worth it for me to buy a code reader? Or would my money be better spent taking it into the shop?

minibike132 · February 1, 2010

Your money would be best spent checking the battery and cables first. You're an aircraft electrician so you should be able to do a loaded voltage drop test on the B+ cable to the starter. Pull the fuel pump relay in the under hood electrical center so it won't start and do the voltage drop on that circuit. Then do the same for the negative cable. The battery should be tested with a real carbon pile load tester not an electrical one. If that all shows good move on from there. If the vehicle isn't getting the necessary voltage silly things start happening, even a loss of a volt can make some of the data circuits go a little goofy since they run off 5v. If the 12v circuit is only producing 11v and it is supposed to be stepped down to 5 it would actually be more in the 3.5v range which can cause lots of issues.

raptorman · February 1, 2010

i'm just trying to plan for possibilities. Of course I'm gonna check the battery and cables before I go spend any money, I'm just trying to get an idea of what I should do after that if it turns out the battery and cables are fine. I already put an alternater in it, going to test battery and cables when it gets back, then I need to get diagnostics done to check for computer problems. You know where I can get detailed schematics online?

minibike132 · February 1, 2010

I'm not sure where you could get shematics, it all depends on the schematic you are looking for. There are hundreds for this vehicle. You kind of need a direction to go before looking for an appropriate schematic. After you verify the battery and cables check the voltage to a bunch if not all of the fuses. If you have an ignition switch issue clusters of fuses are going to be low on voltage. Or you could go directly to the switch and verify all the power circuits with a sealed beam lamp to simulate lots of load on the circuits. That is the way I go.

Start there, the way the cluster has info delivered to it is a bit complicated for me to explain unless it gets down to the point that it would make sense to get into that.

Have the vehicle scanned for codes, I would suggest trying to find a dealer or a shop with very good equipment that can check all modules not just the PCM that would just pull all module codes for cheap. It doesn't take more then a few minutes to pull codes and write them down. Usually cheap scanners and the ones that you get auto zone to read for free only do PCM and sometimes ABS. That may or may not be helpful.