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Chevy Silverado and GMC Sierra Electrical and Computer Questions



  • don't know if it will help or not, I had a problem somewhat like yours. truck lights work fine, but no running lights on my horse trailer. funny thing was my turn and stop lights on the trailer work fine. come to find out i blew the fuse in the truck for the trailer running lights. replace fuse and all works fine
  • He guys I have a 03 gmc serria 2500 hd 4x4 and wanting to install that second batery, My brother was looking and buy the exact same truck except a 2000 and i noticed it had the second battery. Any information of how to go about the wiring would be great. Im sure if I took the time id figure it out but me and wiring dont go together to good unless i have a box of fuses. thanks
  • hi
    i have silverado 99 extended cabien. there is a message in message center "cargo lamp on" but it is not working. also, interior lights not working also. please help me to get solution. fuses are ok.
  • obyoneobyone Posts: 8,054
    did you check the bulbs?
  • No, but all the lightes stop working at one time and the indication on the message center appear.
  • On the inside of the truck there is a relay center.The relay is marked(on the relay cover)as the inadvertent power.That is the relay in the courtesy light circuit.You can swap it with the one out of the Tahoe.The relay center is on the firewall above where yout left foot would be.Make sure you swap the bcm's back to the proper vehicle the vin is stored in there and will cause problems.That's if it didn't already.
  • hey guys i just bought an 06 sierra 1500 and so far im loving the truck 5.3 4x4, but i noticed when im raising a window with the power switch all the instrument lights get real dim and i can see the headlights seem to dim somewhat also, is this normal from power windows or is this an electrical issue?
  • To give everyone an update on this ( sorry for the long delay on this)......... As it turned out, there was a light in the "cluster" above the bed that had burned out. I replaced every bulb on the exterior of the truck, with this set being the last set. Once that set was replaced, I had no more issues with this.
  • That does not sound right. You may have a bad motor or some type of problem from the factory with the wiring.Is the window straining on the way up? I have had several power windows fail in my 2000 and 2003, the problem is usually a broken transmission mechanism ( cables, etc.). Our winters likely don't help as it is normal for the window to freeze. The problem has not been the motor, nor do I recall the lights getting dim. If it's still under warranty, take it in and I am sure they will replace the mechanism and possibly the motor, it is common warranty failure.
  • thanks for replying, no the windows do not strain going up, do you think this is a major issue something that could possibly be a huge problem till i get it in, or is it just something minor?
  • 2004 silverado, left turn signal on(only left)and hazards flashed. Hear its a common problem, well I did some research online and it turned out to be an easy fix. All I did was replaced the flasher behind the fuse box and it solved the problem. Was surprised how much the flasher costs though, it was $94 at dealer but you can get it at for $52. New flasher also has different Delco Part # then stock # and sounds much stronger when flashing. Saving receipt cause i see a recall in the future.
  • My 2000 GMC sierra has a short somewhere and I can't seem to find it, The fuel pump went out and I changed it out with a new one, but now the PCB 30 amp fuse keeps blowing. I would replace the fuse then the fuel pump would work and keep going and now the fuse keeps blowing and i have well i think i have messed with all the wires but still can't find anything wrong. HELP please

    :cry: :cry:

  • I am having trouble with a 99k1500 that is starting and stalling. I believe it is the Passloc system, so I have went in and put a resistor in in place of the key. Key measured 2350 ohm I used a resistor pack of 2357ohm. However I am still having the same intermittent problem. I will do the 10 minute key on relearn this evening, again. If it still persists what are the thoughts for a bad BCM? And can I just get a used one and pop it in or does it need to run a relearn of some sort? What is the preceedure? thanks for the help
  • My truck...sitting outside... All of a sudden, the truck chimes..and lights blink AS IF...I was pressing my remote to lock the doors. This goes on, intermittently every other minute or two. I eventully have to disconnect my battery to stop it.

    Is it a fuse? HELP!!

    (2006 Silverado 2500HD).... dicemd at
  • Can the backlights for the steering wheel controls be changed? I have had almost all of mine go out one by one over the past month. It seems like each switch should have its own bulb but I can't figure out if you can replace them or not.
  • i bought a '95 gmc sierra 2500 that needed a new engine. when i bought it, the engine light came on. my mechanic friend changed teh engine with a 2000 rebuilt engine. its a 5L 305, however, after changing the engine and swapping some parts around the engine light is still on. he states teh engine runs great and he looked for codes and the code for the electronic spark control module came up. he looked for the module and says he found it integrated with teh computer, however, he says the truck is a '95, but the wiring harness is factory installed and for the yrs 96 - 2000.

    does anyone know how to get my engine light to quit flashing when only that one code comes up for the module or what the problem is??? and if i, as he is suggesting it may be the computer, what yr/truck do i get teh computer from???

    he says he checked the vin with chev and with his code reader and both say its a 95 but he can't figure out why it has a ;96 - 2000 wiring harness.

    any replies would be appreciated and can be emailed to me if possible to,


    mike d
  • grampy1grampy1 Posts: 140
    2004 Sierra,auto,4.8 lit. work truck.

    Does this truck really have the mileage reminder for oil changes that
    notifies you when its time to change the oil? :confuse:
  • Hello,

    Can you tell me what fixed your truck, I have the same problem with my truck...


  • Upon start up, engine would run very rough, excessive noise, no power or rise in RPM's upon pressing gas pedal. Checked oil and it was low so I replaced it as I heard there was a sensor that wouldn't allow engine to run normally. This didn't help. The weird thing is if I start the truck, turn it off, drive at idle 3-4 times, off, on, off on, you get the picture. It will run fine for the rest of the day. Then the next mornig, I do the process all over again. Fuel filter was replaced about 10k miles ago. I have opened the wing nut on the bottom of the fuel filter in case there was water in the fuel. Any help would be helpful as money is super tight right now. The check engine light is on when it runs bad, then it will go off when it is running good. Thanks
  • Last week I had the throttle body replaced. Brought it home and parked it until today. My 2003 silverado is doing the same thing it did before I replaced the part. Do I need to drive it more, or something to "reset codes"?
  • I have a 2001 GMC,Sierra, 95K. Recently outside mirror adjustment control stopped working. In past, controller has on a very few occasions not worked or at least was intermittent, but always finally did work. Yesterday found that it was completely dead. No response at all.

    I will check fuse. Where will the fuse be located?

    If fuse is not the problem what else should I look at?

  • I have a vintage 1993 Chevy Blazer K1500 that still runs like a sewing machine after 235K miles. But today, the temp gage went [non-permissible content removed]$ up. That is, it reads off the high side of the gage even with the engine is stone cold, ignition switch on or off. The computer has stored a code "15". I followed the Haynes manual recommendation to remove the glovebox and wiggle the connectors to the computer, no change. I unplugged the engine coolant sensor connector, no change. Do I have an open or a short? I hate electrical issues. I was planning on replacing the sensor, which may happen tomorrow, but I fear the problem resides somewhere behind the instrument cluster. has anyone in the Silverado forum encountered a bad gage problem like this one?
  • I purchased a temp sensor, but the connector had a different pin arrangement. I took it back to the auto parts store who showed me that the 350 TBI has two coolant temp sensors, one for the computer, and one for the gages. The one close to the thermastat is for the computer, while the one tucked back near the firewall is reserved for the gages. I'm going to replace that one tonight.
  • elentzelentz Posts: 5
    Hi, Checking to see if anyone has heard of a fix, bulletin, idea about my problem. The 2 WD ext cab PU has the 4.8 V8 auto and 175000 miles. During very cold weather, below 28deg F, the charging system has intermittent temporary failures which look like momentary dips on the charging meter and looks to oncoming traffic as if I am flashing my headlights. The failures are never more than a few seconds at a time. I have checked for loose wiring, have replaced the battery and alternator. Still have the problem. Is there a particular component I should check that might be exposed to the elements and not quite work when cold? I have been unable to find a similar problem on this forum, except the ignition switch guy, and I don't think this is the problem.
  • 2002 Chevrolet Silverado 1500 4x4 Z71 5.3 Vortec
    Engine. 109000 miles. Only on cold mornings/days
    does it stall and idle really rough and missfire. Here is the strange part: if I unplug the MAF sensor, it runs
    fine. If I plug it back in, goes right back to crap. So I
    thought i had found my problem and replaced the MAF Sensor but to my surprise it did the same exact thing. It is throwing a coolant temp sensor code so maybe
    that is the culprit. My question is if it is a bad coolant temp sensor, why does it run fine when I unhook the MAF? I also tried unplugging the coolant temp sensor but it still does the same thing if the MAF is plugged up.
  • Hello folks, first time here or on any forum for that matter, my chevy passenger side window, seat heater and both of my auto side view mirrors stopped working. i have been through all the fuses, all look good i was hoping to get some info before i spend lots of dollars, Thanks
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