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Chevy S10 - GMC S15 and Sonoma Electrical Problems



  • Where would i find the ECU on a 97 s10 pickup LS?
  • gonogogonogo Posts: 871
    Not sure on a 97, it is either under the hood on the passenger side or behind the glove box.
  • I have recently bought a 99 Sonoma SLS, my problem has to do with the brake lights. It's seems if I turn off my truck under low light conditions, my brake lights, on the box (not the one above the window), remain on. I checked the bulbs, they are the correct ones. I am thinking it may have something to do with the automatic light sensor. Anyone else run into this problem?
  • madmattermadmatter Posts: 2
    edited February 2010
    Hi, this is my first post!
    I drive a 2000 Chevy S10 with a V6 motor. The truck has issues. Over the past 3 years there have been 5 one week periods where the truck does not want to be started. Here is a rundown of what happens.

    First I open the truck door. Then I sit down and close the door. I turn the key sometimes I turn it fast and sometimes I turn it slow. While turning the key slowly the truck goes through its normal starting phases. It shuts off all the unnecessary electrical systems, then right before the engine turns over it gives off one, two maybe thirty clicks (think video game machine gun sound) then the truck dies.

    When I say the truck dies everything goes out it loses all power. The horn doesn't sound, the power locks don't work etc. Once dead the truck demon does one of two things. It may flicker all the speed/rpm/gas gauges then a few seconds later it magically turns on or the truck stays dead. The truck stays dead for up too two hours before magically regaining power.

    The weird part. If the truck stays dead and I connect it too another vehicle via jumper cables. This seems to give it a better chance of a successful start (although the battery is fine) And even when connected via jumper cables it may still die, but if I wiggle one of the jumper cables, the truck instantly snaps back to life for me to chance another start. It takes an average of 20 start attempts before the truck will start and that's with or without the jumper cables.

    So an overview of the Electrical Demon, I turn the key, the truck dies (electrically dead), I either A wait or B fiddle around with the battery connections to try and arouse the truck back to life. Once the truck regains electrical consciousness I turn the key again cross my fingers and hope it starts. If I don't turn the key to the start position, the truck is usually fine (although not always). If I use jumper cables the truck seems to respond better by starting sooner. It takes up to 30 tries for a successful start. Once it has been started successfully It runs fine until I shut it off.

    Need Good Advice Soon Sincerely,
  • the_big_althe_big_al Posts: 1,069
    If you say the battery is good, then I would look at the battery cables. It sounds like what you are describing is actually a bad battery, or the symptoms of a bad battery. So if your battery is indeed good, then look at the connections. I suspect this is your problem because you say the truck runs fine after getting it started so the issue isn't with the alternator or the connections after. It is between the battery and the starter. Even if the cable looks good, there still might be corrosion inside the cable that is not visible. Check there first and see if that solves your problem.
  • When I say the battery is fine, I mean to say the battery is charged. It holds a charge fine, but I am unsure if the battery has some undetectable issue (internal short-circuits) or if the cables are corroded on the inside. Everything appears to be fine on the outside. I did have an amplifier and a new CD player installed two years prior. The amp is 200 Watts which is very small in my opinion. I do not know if this installation is somehow related to this problem since this problem existed before the amp was installed.

    Some other magical happenings with the truck:
    1. The lights inside and outside the truck flicker with the music on the radio.
    2. The lights inside and outside the truck flicker even with the radio off.
    3. When the gas gauge is below 1/4 of a tank the abs light comes on. There is no problem with the anti-lock brake system. The sensor is incorrectly working and seems to be correlated with the gas gauge in some way.
    4. The horn works half of the time, when they test it in the shop it works and when I need it on the road it doesn't. The shop said the horn was fine. I know from experience that is only fine when it wants to be and when I want it to sound it refuses.

    If you were to witness all these events and know the truck as I have come to know it you would be certain it was haunted. This truly is not the case but the issue seems more complex than the cables being bad (although it would make sense if they were. The battery could be bad but this is the second battery in a row that has been faulty. I'm wondering if the truck could make batteries bad or if batteries are bad before they are put in the truck.
  • the_big_althe_big_al Posts: 1,069
    edited March 2010
    Hmmm... I still lean towards cables. At least as a place to start. A bad cable connection can cause a battery to go bad. You might also have a bad ground somewhere. That would cause lights to flicker when a load is placed on them - i.e when your radio is on. A bad ground would also cause lights to flicker with no load placed on them. Check you major grounds. A bad ground wire from the battery to the starter is one place to start. Also check the ground from the alternator. I'm not an electrical genius and I am pretty much shooting in the dark, but if there are several systems going wonky, then I would check at the main sources of power - the battery and the alternator. You could have a bad alternator too. That won't help with the starting issue because that is a battery only system, but a bad alternator could be causing the flickering too in that it won't be able to keep voltage up when a load is placed on it. It could also cause a battery to go bad in that it doesn't send enough juice or amperage back to the battery to charge it fully... It's a vicious cycle. Check cables. Replace them if needed. Have the alternator checked out. It's not uncommon for them to go bad.

    I have an amp on my system and have had for about 5 years and have never had a flickering problem. I had a 500W amp and now a 250W amp and the lights don't flicker at all when the truck is running and only slightly when the the truck is off. Make sure the amp is properly grounded to the frame or floor of the cab. I am on battery #3?? Maybe #2 since I have owned the truck (7 years) and alternator #2. The only time I had an issue was right after I put in alternator #2 and the cables weren't tightened properly. I had starting issues exactly like you described. I cleaned all the connections to the battery and the tightened them all up and haven't had an issue since.
  • agrivateragrivater Posts: 2
    edited March 2010
    :confuse: I have a 99 chev S-10, it fires up and runs for about 2 seconds then dies.. As long as I squirt starting fluid into it it will continiue to run, and before yu go to the obvious. It has great fuel presure!! Something is telling it to shut the fuel off..

    My "security light" flashes 3 long single, followed by 2 quick tight flashes.. Does anyone kno what this code is trying to tell me?? Or does anyone kno where I can find a list of the code definitions?? :sick:
  • I have a 99 chev S-10, it fires up and runs for about 2 seconds then dies.. As long as I squirt starting fluid into it it will continiue to run, and before yu go to the obvious. It has great fuel presure!! Something is telling it to shut the fuel off..

    My "security light" flashes 3 long single, followed by 2 quick tight flashes.. Does anyone kno what this code is trying to tell me?? Or does anyone kno where I can find a list of the code definitions??
  • gonogogonogo Posts: 871
    This thread tells you all the fixes for the security won't start issue, you like to read.
  • c2cpc2cp Posts: 11
    I noticed that there is water leaking somewhere around my fuse box under the dash on the drivers side. does anybody know how i can unhook the fuse box from the wall? or has anybody else had this problem?
  • Well I seemed to have solved my problems, I discovered I had a loose ground coming off of my battery. I tightened the connection and my issue has disappeared. :shades:
  • mgjameianmgjameian Posts: 1
    edited May 2010
    My wife's 2000 Chevy S-10 wouldn't start, after sitting for a couple days. I connected jumper cables to her battery and the engine cranked without putting the keys into the ignition switch. Is this a starter, ignition or alternator problem?
  • dave8697dave8697 Posts: 1,498
    It has a lighting problem. No dash or radio lights at night. The radio lights up in the day. When I first got it 3 years ago, there were no interior lights so I got a new headlight switch. When I put it in, I had dash lights for 1 second and then they were dead again. The switch fixed the interior and dome light problem. I ended up mounting a small 3 led light strip wired to the extra cig outlet. I point one at the tach, one at the speedometer, and the 3rd one at the radio and vent panel.

    I also had a water leak that showed up in constant wet carpet and I couldn't ever find it. One day I was pulling up the carpet and was running the hose all around the rear window, the 3rd brake light and then hooked it under the windshield wiper and let it run for 30 minutes. No water ever came in by the pass side footwell where it always got wet. I gave up that day. It turned out that I fixed the leak. By flooding the vent cavities by the w/s wipers, I must have floated away som leaf or something that was blocking a drain port. It allowed the cavity to stop overfilling and somehow backing up into the cabin. Been totally dry for 2 months now. I pulled out the console and seats and dyed the carpets black right after that. It came out nice. I mixed a 39 cent box if dye in an empty spray bottle and just sprayed it and rubbed it in with a washcloth.

    Also had the intake manifold gaskets replaced by a local mechanic. They were bad at 111k miles. Common on 4.3 L at 100k.

    Now I need new front tires and I might have the same mechanic fix the a/c.

    My last tank of mixed driving was over 21 mpg with lots of congestion on I-70 due to construction. I was about to dump it over the water leak problem.
  • the_big_althe_big_al Posts: 1,069
    you might be blowing a fuse for the dash lights, or there is a bad ground somewhere... electrical's on these vehicles (or any vehicle for that matter) are terrible gremlins to get and track down once you've got them.

    I can attest to the intake manifold leak. Mine did that too and a buddy andn I replaced it at about 130K miles, although it had been leaking for several thousand before it finally went all the way and started dumping coolant down the front of the block....
  • dave8697dave8697 Posts: 1,498
    I punched it coming off an interstate ramp a year ago on a icy morning and when I parked it at work it was pouring coolant onto the ground. Stop leak never really worked and the leak got worse this spring. It was $400 well spent. Lucky I didn't freeze the water jacket this past Feb. because keeping a 50% mix was getting expensive. The mechanic I used was 1/2 mile from my house and beat the Chev dealer by $290 on price.

    I gave up on the electrical problem. I looked at wiring diagrams but there are multiple buried relays and the day/night sensor could even be part of the problem. I even put in a new dome light and brake light. The red 3rd brake lens gets a split from sun or heat from the brake light bulb, and water gets into the wires there. There have never been any other electrical issues. The Sonoma battery terminals don't corrode like my Astro.
  • johnstajohnsta Posts: 1
    I have a 98 s10 pickup and i am having a problem with my high beam indicator. My high beams work fine but my high beam indicator doesn't turn on and off. What i don't understand is that if i just turn the key to turn the power on the indicator works fine. Once i turn the truck all the way on it stops working. Any help would be greatly appreciated, my inspection is out and where i live that indicator has to work to pass inspection.
  • fireman46fireman46 Posts: 1
    edited July 2010
    I have a 2002 Sonoma Pickup. Can anybody tell me what the proper reading is for voltage gauge? Mine used to read on 14 or bit more. Now it reads less than 14. Had it checked everything is normal but I still feel its not right. Can anybody help. Thanks.
  • the_big_althe_big_al Posts: 1,069
    The voltmeter should be reading right at about 14 amps (straight up in the middle) while the truck is running. If not, it either means faulty gauge or faulty alternator. If you had it checked the test should have shown that the alternator was drawing about 14 amps. If it reading less, than it is not working right and a sign it is going out. Another good test is to see if the head-lights dim while the stereo is running or when you turn the AC compressor on.

    I have a 10" subwoofer I am running in my truck and I can crank it without affecting the lights while the truck is running. Simple setup, no caps so it draws all its power through the alternator.
  • gonogogonogo Posts: 871
    Mine runs in the middle or above if it sets too long.

    "Everything checks normal", do you mean at least 14 volts at the battery with headlights high beam on,HVAC blower an AC on, radio on with 1500 rpm.
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