Please help

[Danielgreig]

I'm not sure where exactly to post this but anyone's help will be greatly appreciated. I know there might be a lot of useless information I'm posting but I hope anything can help in figuring out the problem. Last night after a long drive on our way to family vacation we stopped at a restaurant to grab some food. When we were ready to leave I tried starting the Tahoe and it cranked on for a second and then shut off. Tried it again and same thing. I checked the battery and it seemed as if the ground was a little loose so I was able to tighten it. The drive information center is now saying "unknown driver" instead of the typical "driver 1" on start up. It still won't stay on for more then a second. The key fob, the interior door locks, windows are not responding, and the interior lights do not come on while the door is open. I can manually turn on the dome lights and headlights work fine as well as it does not struggle to crank on. It just turns itself of immediately. It has a new Optima yellow too installed only a month ago. I am thinking it has to do with the stock security lock out or what ever it is called. I was able to get a ride the rest of the way and left the Tahoe in the parking lot overnight and it pained me to do so. I will be getting it towed to the cabin today and have some basic hand tools to see if I can get it started. I think when it arrives, I will try to disconnect the battery and then reconnect in the hopes that it will reset and be back to normal. After that I am out if ideas so if anyone knows a trick or what the deal is, I'm all ears. Need to be able to drive it home in a few days....... Thanks in advance for any help.


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[OR VietVet]

I agree with your assessment of having to do with the security system. It may just need a reset as you suggested. Unhook the battery, both cables, leave it for about 30-60 minutes, go have some vacation fun, reattach cables after making sure all connections are clean and there is no corrosion swell under the cable insulation near the cable ends. The fact that it did not recognize you after tightening the cable leads me to believe it is in default mode after you did that. Simulating someone messing with the battery, so to speak. When ready to start, use the other key and fob if you have it with you. I mean lock and wait 60 seconds and then unlock the door with the fob and then try using that key. You may have a problem with the "chip" in the #1 key and fob. Good luck.

By the way, as I have been begging for on here, you shared a concise, chronological, detailed list of your problem and that made it way easier to read through and follow. Wish all who asked for help did that.

 

[Danielgreig]

Thanks raiderron for your response. I will try that as soon as the truck gets to the cabin. Also, I only have the one key and fob. I can try what you suggested with that one correct?


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[OR VietVet]

Yes you can but you should have at least a hidden chipped key on that rig at all times. You dummy! LOL! Smack yourself or have the wife do it for me! Not recommending the fob being hidden because the elements can damage it but a key in a magnetic holder can be a life saver.

Now go have fun Grasshopper! LOL!

 

[Danielgreig]

Thank you so much raiderron!!! It worked and I am back on the road. You are one of the reasons I love the community here on this forum. You have been very helpful and my family and I are very grateful for your help.
BTW...... I had my wife give me a good smack.....lol.....and when we get home, I will be getting some extra keys and fobs made.


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[OR VietVet]

Thank you so much raiderron!!! It worked and I am back on the road. You are one of the reasons I love the community here on this forum. You have been very helpful and my family and I are very grateful for your help.
BTW...... I had my wife give me a good smack.....lol.....and when we get home, I will be getting some extra keys and fobs made.


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Yea, it had that loose connection and maybe even dirty and the system didn't like that. You then tweaked it and it liked that even less. Hope you can still have the fun you wanted for the weekend. Enjoy.

I hope she didn't hit you too hard! By the way, remember, don't keep the extra fob on the outside of the rig. Use the extra key, if needed, to unlock the door and you can hide an extra fob inside if you want to. When you have the key outside for awhile take it out and make sure it works periodically, same with the fob. Merry Christmas!

 

[SLCHOE]

Why did you replace the battery?

Is your alternator charging properly?
The reason I ask is because people frequently replace the battery when things start acting up but it's their alternator that has really given up the smoke (i'm a mechanic, i see this all the time). They put a new battery in thinking that was the "cause" and a few weeks later have the same issues.

 

[OR VietVet]

If he replaced the battery over a month ago, for whatever reason, and the alternator was really the problem, over a month ago, then he would have had whatever problem he was experiencing long before now and it is a moot point. If I buy a used vehicle and don't have maintenance records then I do all fluids and if the battery looks old or the date stamps are old or the date code on the side is old I replace the battery to be at a starting place so I don't get stranded with a vehicle I don't know enough about. Roadside assistance is way more expensive than just putting in a new battery for peace of mind. Especially if he already had this trip planned and was just doing his due diligence to be prepared.

Or it's whatever you were leaning towards?

 

[SLCHOE]

If he replaced the battery over a month ago, for whatever reason, and the alternator was really the problem, over a month ago, then he would have had whatever problem he was experiencing long before now and it is a moot point. If I buy a used vehicle and don't have maintenance records then I do all fluids and if the battery looks old or the date stamps are old or the date code on the side is old I replace the battery to be at a starting place so I don't get stranded with a vehicle I don't know enough about. Roadside assistance is way more expensive than just putting in a new battery for peace of mind. Especially if he already had this trip planned and was just doing his due diligence to be prepared.

Or it's whatever you were leaning towards?

Slow down there chief. Just because his battery lasted a month doesn't mean his alternator is not a cause. There are a few ways an alternator can fail. One of them is where the rectifier bridge faults and the alternator intermittently causes the alternator to actually become a LOAD on the electrical system. I've had vehicles that threw numerous codes for numerous separate bussed systems and most shops would fault the ECM as the cause. Problem is when the ECM is not getting proper current/voltage from the alternator, it does funny things.

I had a vehicle just like this hooked up to the Midtronics GR8 and watched it go from a static voltage of 12.5 to a charging voltage of 14.3. All is good right? 4 minutes into the test at idle, it dropped down to 11.1 volts for a duration of 20-30 seconds then corrected itself. At 11.1 volts, it was actually lower than static battery voltage (key off engine off battery voltage).

What does that mean? The alternator, which is supposed to "charge" the battery at 14.2-14.6 VDC is actually causing a load that drops down the voltage below the static voltage of 12.5.

This is basically like leaving your headlamps on in a parking lot except worse. It happens without you knowing it cruising down the road.

Moot point? I think not.

Ami I saying this definitely is the cause? No. It's something to look at.

 

[OR VietVet]

Came off wrong. I agree with all of the scenario but have never in all the 35 years of running shops seen a problem that he may have had over a month ago and replaced the battery because of it, trying to fix it, rear it's ugly head over a month later. I know all about rectifier bridges and diodes causing loads on systems simulating a load like leaving the headlights on. I have used that explanation with customers many times. I also know that typically, meaning over 95% of the time, the ECM is not the problem even though unqualified techs will point at it because their head hurts from all the scratching they do because they are lost in the diagnosis.


Valid comeback about the moot point dig. I felt I knew I was right about his problem. I have also had a couple of Coronas watching myself win the Chargers/49ers football game and I was quite happy about the extra $50.


I have ran across his problem before and while I cannot say it is an exact reason for his problem since I am not there with equipment, I felt real sure about what I told him to do and I hope it stays that way and gives him no problems. I mean after all, he got smacked in the head by the wife because of me!

What I really like about your comeback is the details. So many times there are none. Thank you for them. Apologize if offended but sounded like I didn't. Looking forward to more help from you SLCHOE. By the way, thanks for calling me "Chief." I was in the Navy during the Viet Nam War but never made Chief. Adios!!!!!!!!!!!!!