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GMC Jimmy Electrical System


Anyone out there have any tell tale signs of how to know if you alternator is going, I have a gut feeling that mine is going but no way to prove it, anything helps.... ps after I deal with this issue I will be installing my 2nd set of front hub and ball bearing assembly, you think a recall would be done or some kind of class action suit against this makes me sick oh well....


  • repairdogrepairdog Posts: 948
    Your battery will start to slowly discharge as the alternator fails - or be dead one morning. Often you will hear it crank slower on start. Test with a volt meter at the battery - 12.6 volts off and then running 13.5-14 volt range from alternator. Also look at the gage and it should show that same 13.5-14 range running. Avg 80k mileage for one. Hubs should last 80-120k also on avg. There are a few cheap brands or economy hubs on the market that fail faster for about $110 each. The TRW and BCA ones are over $150 each.
  • Hello I'm having some new issues with the turn signals on my 2000 GMC Jimmy SLT 4DR. they stopped working today all together. I figured maybe a blown fuse..checked #10 turn signal 20amp fuse looked fine..switched it anyway..still no turn signals at all. anyone know where to check first? I'm thinking maybe the turn signal switch, it seems to work ok for high beam after it glitched a bit. also I have an intermittant problem starting where it won't stay running then fires this has happened maybe 6 times total.
  • repairdogrepairdog Posts: 948
    Blinker flasher can behind the glove box - try that. Separate circuits for emergency flashers (work on brake light) and blinkers (separate bulbs). Any new trailer wiring recently installed? Does the security light flash after it stalls (put key in run and it should go out in 5 sec)- if it keeps flashing have GM check the passlock system.
  • Hey Repairdog,
    thanks for the reply, I found the flasher behind the glovebox in the lower RH corner, apparently somehow my hazard switch got bumped when I trip the hazard switch one way I have my turn signals back and can feel the flasher clicking but in other position I have no turn signals or hazards I can feel the flasher relay click slightly when I engage the hazard. any idea if the same flasher relay runs the hazards as well, it appears maybe that part of the circuit is malfunctioning.
    Re: starting issues it has a trailer plug in that has been on the truck since my dad bought it but no recent additions not sure about the security light I tried turning the alarm on & off when it occurs but doesn't seem to change anything.
    my dad passed away last year so unfortuantly I can't ask him anymore. I saw someone mention the key switch on one forum, but it happens so randomly it's wierd.
    thanks for helping out I was suspecting the turn signal switch assy maybe I just need the flasher/hazard? relay
  • today I went to start the Jimmy and the ignition key cylinder locked up on me with the key inside the lock. I couldn't remove the key or lock the power locks so no way to lock the hatch in back manually. after removing the lower dash and steering column plastic I noticed a cap on the lower column plastic cover after removing it there is a gold colored pin upon depressing it I could remove the key. intially the jimmy still wouldn't start but did eventually tried starting it a dozen more times and it fires up and power door locks function. I'm suspecting the ignition & start switch and ignition key alarm switch (as the service manual calls it) where that gold pin is located I can see it move in & out when I insert the key appears to be some sort of solinoid. any ideas ?
  • repairdogrepairdog Posts: 948
    There is a large pin that locks the steering column but if that starts to jam a simple wheel shack usually frees it and then the key has I believe 4 pins in the locking cylinder that the key lifts up to rotate the tumbler.
  • Well after being stranded because it wouldn't start, Just when I was about to let a dealer fix it, I called AAA and the driver suggested we jump it,( I didn't think the battery was the problem it has about a yr old red top Optima in it) it fired right up. I get home put a voltmeter on the battery and get a reading of 12.5 volts with the Jimmy running. thinking the alternator went bad because I wasn't getting a 14 volt reading, I went and bought one and a new serpintine belt. I go to pull the battery to put it on the charger while I'm doing the alternator install.
    the culprit to my problem becomes apparent the plus side battery terminal was ever so slightly loose and had some corrosion that wasn't apparent from the outside, but it was just enough to give me a bad connection and intermitant problems. feel somewhat stupid I didn't find it before that
    but thought I'd pass on the info.
    the Jimmy didn't act like it was a battery ( no clicking solinoid or slow cranking or the usual symptoms )
    I cleaned the terminals with some baking soda & water and then rubbing alchohol put some new anti corrosion washers on. and wala 14 volt reading on the voltmeter without changing out the alternator (with the Jimmy running).
  • When using the right turn signal on my 99 Montana all six bulbs blink faster then normal. When the brake is applied the brake and running lights go out and the blink speed goes to normal. There are no blown bulbs. Where should I start?
  • Hey maybe you can help me out? When I go to start my car, it cranks, but it won't turn over. It just dies. It's definitely something with the security system because the security light comes on and it dies as if I was trying to steal it. I tried activating and deactivating the alarm, but that doesn't work. Also, this doesn't happen all the time. Only when it feels like it, I guess.
  • Well I thought for sure my security system was to blame, on several occasions I tried to start it and it acted up.
    check your battery connections, unbolt them and make sure they are clean without any corrosion if corroded clean with baking soda and water an old toothbrush works good to apply and scrub it clean, I added some anti-corrosion washers from the parts store. my positive cable was ever so slightly loose combined with the corrosion that had formed it was enough to cause me intermittant starting problems and eventually a charging problem. its simple enough and doesn't cost much of anything if thats the culprit.
    if you have a voltmeter check for 12 volts at the battery cables, and you should see about 14 when running.
  • Yes, good advice to check the terminals and the battery itself. Also look at the starter if it does not crank over at all there is an ignition wire to the starter that may have a loose nut holding it on - seen that one. If it does crank over but not start post back and a whole diff problem.
  • I do not track Montana problems so as a general GM area look/research the hazard switch or flasher button on top of the steering column, the multifunction switch (the tyrn signal arm and the controls in the column, or the brake switch on the brake pedal - only ideas. Do some searches and good luck GM may have a bulletin - call the dealer with your VIN and ask - service can pull this up.
  • Ok everyone I'm someone can help here. I have a 2002 Monte Carlo and my security light stayes on now and my car seems to start only part of the time and other times it won't even act like it will start everything comes on but car won't start. I was told I need to reset my security light but I have no clue how any clue or hints will be very appreciated.

  • If same as blazers Passlock was activated and its a body computer code that requiresa scanner to reset so dealer time. Its probably that if after you turn the key to run (not start) and the security light does not go off after 5 sec buts stays on.
  • I am trying to replace the third brake light on my '02 Jimmy. Of course you can't just replace a bulb on these ones, you have to buy a whole new light. I have the new one and I have made sure that it is the correct replacement.

    Does anyone have any instructions on how to replace this light? Most importantly, how to get to where the wires "plug in"?

    Thank you
  • gitmogitmo Posts: 23
    Lately it's taking about three or more attempts to get my Jimmy started. It turns over but not even close to ignition until the third or fourth try. Also, while driving there is a high-pitched whining sound that comes and goes as the accelerator is applied. it's had a new battery and alternator, serpentine belt installed. Fuel pump has been replaced. i've also noticed a burning plastic odor as well lately.
    Any help would be very appreciated, thank you.
  • gitmogitmo Posts: 23
    hello again. Also lately I've tried to put the truck into FWD mode, I press the dash button, the light blinks a few times but it never engages. Any ideas on this latest of woes. The truck has 101000 miles on it. 2000 GMC Jimmy SLT.
    Thank you :cry:
  • This could be many things. Tuneup with a new cap/rotor, wires, plugs is #1. Then air and fuel filters. Any codes to point to a sensor? If the smell is more like burnt maple syrup kind of it could be the coolant leaking or a heater core - check the reservior for a stable level, look at the water pump for leaks and the whine, see if noise is from the AC compressor with AC or defrost on, look at the vac lines underhood drivers side for rot, and good luck you have to narrow it down.
  • Depends on 3 or 4 button system and do a search on 4wd and many posts there.
  • This is an interesting one and I am wondering if anyone out there has any ideas. I have a 1999 Jimmy SLE w/ 96K. I bought it used a few months ago. The issue going on is this. I will be driving and with no build up or indication, all of the instruments (speedometer, tach, oil, temp, gas, etc) on the dash will fail to zero. The vehicle will not shut off and the instruments will return to normal after about 3 seconds. This has happened to me three times while in cruise control but it just happened to my wife while driving in the city here (no cruise).

    There are many other things such as the heater fan doesn't work in position four but does work in position 1 - 3. (That just began a few days ago). I am looking for wiring diagrams for this but don't know where to find them.

    Anyway, if somebody has an idea about the instrument failures, please let me know.
  • I had the same problem with a 1998 GMC Jimmy and spent thousands of dollars on troubleshooting electrical. But the problem all along was a bad ignition switch. any other questions let me know my email is [email protected]
  • cairnscairns Posts: 4
    On mine I cut and resoldered the wires. The used heat shrink tube to seal. Do a nice small job, that way you do not have to dis-assemble the truck to get that job done.
  • lisa40lisa40 Posts: 1
    Purchased a 1995 GMC Jimmy from an individual - said they had no problems...... but, next day it started cutting out while driving...since then, have put a new computer, crank sensor, air temperature sensor, fuel regulating swith, new fuel pump, and new fuel tank. It sometimes starts for a few seconds, sometimes a few minutes, but still unable to drive because it cuts off. Can you offer any suggestions.
  • gitmogitmo Posts: 23
    Have you had the fuel injectors checked? Mass air flow sensor? Is it six cylinders? Does the "check engine light" come on? Has it come on at all? If it does, have the codes read by your mechanic, or a local Autozone will read the codes for free. It could be an electrical problem as well, maybe a bad harness sending to the injectors.
    Good luck
  • repairdogrepairdog Posts: 948
    CPI and nut kit is the injection under the intake so look that up - usually smell gas or see on dip stick. Then I would change the cap/rotor to rule out. Check wiring for any cuts.
  • jg85jg85 Posts: 3
    My Dash, the lovely Digital type goes out and comes on of its own free will. It works sometimes but mostly don't, only thing that does it the spedometer, odometer, and the warning lights. I have the Haynes book for it (it has about a hundred other suv's/trucks in it) but it doesn't say how to remove the digital one. I was thinking maybe a loose connection because I have a lot of rough dirt roads to travel to work.

    My ABS light stays on constantly, infact it is the wheel speed sensor that is bad. The only problem with that is that it is riveted in place not screwed or bolted it says in my book. Any advice on how to remove it without doing too much damage.

    Oh it is 4.3l vortec with around 140,000 miles. If that helps.

    Thanks for the input.
  • jg85jg85 Posts: 3
  • meg40185meg40185 Posts: 2
    I've been having problems with the wipers in my 1998 Jimmy. They work, but badly. Delay doesn't always work...if I try to use delay, sometimes the wipers function in the low or high mode, but not delay. When I turn them off, they will keep going for a minute or two, and then stop in the middle of the windshield. It's getting annoying, and since I don't have a warranty, I'm looking to repair them myself. Could it be the motor or the relay? I'm not sure where to start first. I'd appreciate any responses!
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