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2001 Chevy Tahoe Undiagnoseable Electrical Issue
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tahoeopus
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Jan 15, 2010, 9:25 PM
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2001 Chevy Tahoe Undiagnoseable Electrical Issue
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2001 Chevy Tahoe 80K miles, auto, V8, 2WD
For the past two years, the Tahoe will lose its electrical charge and won't crank when you turn the ignition if the car has not been started within the last 16-24 hours. So If I don't drive it for a day the car won't crank without a jump. If I drove it consistently I would not experience any problems getting the car started. In the last few months however the car needed to be started every 6-8 hours for no problems to occur, and after this recent cold spell in south florida it now needs to be jumped every time. There are a few other electical issues in the car, sometimes the radio and A/C would not work for a week or two then suddenly spring back to life and work fine.
Ive taken it to 2 different dealerships and neither has been able to reproduce the problem or find any short in the system. I'm thinking they might have a better shot this time around since the car loses its charge within an hour. I really love this truck and just want it to reliably start. Any help or ideas as to what might be causing the issue would be greatly appreciated.
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Sidom
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Jan 15, 2010, 9:39 PM
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Re: 2001 Chevy Tahoe Undiagnoseable Electrical Issue
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Well with this type of problem, I'm sure it's probably already been done but since I didn't see it in your post I will mention it and that is the battery needs to be load tested to make sure it's good & capable of holding a full charge.
I would probably start with seeing if there is a draw on the system 1st. From what you've posted it really sounds like there is some type of parasitic draw going on. Anything more than 50mv to 75mv is unacceptable & can drain the battery over a period of time.
I know with GMs there were some problems with the BCMs not going to sleep or waking up after powering down causing a draw.
It's pretty straight forward to check it out. Hook up and amp probe shut the vehicle off and take a reading. Sometimes the equipment needs to be left on there for a while even if you get an acceptable draw right off the bat to make sure something down the line does power up and create a higher draw......
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jms8384
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Jan 16, 2010, 9:35 AM
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Re: 2001 Chevy Tahoe Undiagnoseable Electrical Issue
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also anouther thing like with the a/c and the radio is check all the grounds. a dirty ground can give you all sorts of electrical problems. but you need to get a book to find them all thay are all over the car. when you go out to start the car does it crankor just nouthing just a "click click". also anouther this that i am shure was checked but idk is get the alt check out.
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re-tired
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Jan 16, 2010, 2:12 PM
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Re: 2001 Chevy Tahoe Undiagnoseable Electrical Issue
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Since most DIY folks do not own a amp probe or meter nor the background to interpet the readings, i suggest the following . Buy a good test light ,Sears ,Harbor frieght has them .Disconnect batt neg cable at batt . Clip test lght lead to cable and probe end to batt neg mounting spot . While hooked up touch cable end to its mounting point , this will put keep alive cicuits to sleep . With all acc off , key off the light should be out . Have helper open a door, light should come on . It takes approx 75 mv of current flow to turn bulb on . If light is on with everything off doors shut you have aa draw. Check the most frequent culprits - dome lite switch manualy on ,glovebox lite staying on . hood /trunk light staying on . If none of those , pull fuses one at a time and repeat test each time, replace fuse before going to next. When light goes out you will know which cicuit to check .If all check out , try disconnecting alt . YES guys this is 1950 way of checking , but it is doable by the avg person and is reasonably accurate .
LIFE'S SHORT GO FISH
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way2old
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Jan 16, 2010, 3:47 PM
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Re: 2001 Chevy Tahoe Undiagnoseable Electrical Issue
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It is still done daily in shops. I venture to guess we all have done it in the last year. That is a quick way to check for the draw before breaking out the high dollar stuff that most DIY'ers do not have.
Being way2old is why I need help from younger minds
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Hammer Time
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Jan 16, 2010, 3:53 PM
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He'll never be able to distinguish between a 50ma draw that is totally acceptable and a 150ma draw which is not acceptable.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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re-tired
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Jan 16, 2010, 7:12 PM
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If it lights the light its not acceptable if it dont its ok .It works for me . But remember --I am calendar challenged.your way is more accurate thats a fact.
LIFE'S SHORT GO FISH
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Sidom
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Jan 16, 2010, 8:50 PM
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To each their own. I use to use that method all the time years ago with great success...
A test light is a load devise and I have seen them keep modules awake that normally would've powered down and guys chasing their tails. But you have to work with what you have. Definitely wouldn't make sense going out and spending a couple hundred bucks on a tool you're not going to use but then again we don't know what he has in his box.
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Hammer Time
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Jan 17, 2010, 5:27 AM
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I guess we just buy these tools because we like spending money and they were never really necessary. In 1950, we didn't have modules running constantly and the light was a go or no go test. Not the case now and if the poster is looking for a parasitic draw, then he needs a way to determine what exactly he is seeing. Most all vehicles will light a test light these days without even having a problem. It doesn't do any good to save somebody money if it's going to send them in the wrong direction as using a test light will.
I suggest the poster follow Sidom's advice if he wants an accurate test.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
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Jan 17, 2010, 6:33 AM
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Re: 2001 Chevy Tahoe Undiagnoseable Electrical Issue
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This has had a dead battery now so many times it must be junk right now. That and I can't figure the common denominator of A/C and Radio quitting intermittently? There's a clue in that, that escapes me right now,
T
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tahoeopus
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Jan 20, 2010, 4:46 PM
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Re: 2001 Chevy Tahoe Undiagnoseable Electrical Issue
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Took it to the dealership and told them I had a parasitic battery drain, they looked confused and said they would look into it. Battery was fried from so many jumps and had a bad cell so replaced the battery left at the dealership two nights, started with no problems either time. They said they tested the system and its coming in at 35 milliamps so everything is in range and they couldnt find anything but I'm not convinced the problem has magically disappeared.
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Hammer Time
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Jan 21, 2010, 3:38 AM
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Sounds like the problem was the battery all along, should have been tested first.
This shows how testing it properly avoided sending you further down the wrong road. If you had tested this with a test light, it would have lit from the 35ma and you would have wasted a lot of more work chasing false leads.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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nickwarner
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Jan 21, 2010, 10:02 AM
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Re: 2001 Chevy Tahoe Undiagnoseable Electrical Issue
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I guess one question I would have is does this vehicle have an aftermarket stereo with an amp and speaker box? I've seen this problem with a customer who had that setup and let a novice friend install the system for him. Instead of running the amplifier trigger wire to the trigger wire on the deck he wired it to a fused connection that had power constantly. Rewiring this to the deck as it should've been originally solved the issue. He also had to replace his battery for the dead cell from so many starts. Its worth looking at if the problem resurfaces.
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Hammer Time
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Jan 21, 2010, 10:28 AM
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He's already confirmed that draw is in acceptable range. The battery was bad.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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re-tired
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Jan 21, 2010, 7:11 PM
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"Ive taken it to 2 different dealerships and neither has been able to reproduce the problem or find any short in the system. I'm thinking they might have a better shot this time around since the car loses its charge within an hour".
Guess the techs at two dealers should just throw their meters away. Whilst we where playing does too does not. Sidom had the right answer all along ... they did not do the proper test first :
"Well with this type of problem, I'm sure it's probably already been done but since I didn't see it in your post I will mention it and that is the battery needs to be load tested to make sure it's good & capable of holding a full charge"
Sidom wins the gold star on this one..
LIFE'S SHORT GO FISH
(This post was edited by re-tired on Jan 21, 2010, 7:20 PM)
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Sidom
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Jan 21, 2010, 7:55 PM
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You know, I would be lying if I said that I had never overlooked one of the basics & spun my wheels for a few hours only to find out later it was something simple 
We try not to but sometimes get tunnel vision when we think we know the problem going off the symptoms and jump in, in the middle. An instructor of an OBD 1 class I went to had a great saying that I try to remember but sometimes forget "Slower is faster".
Two of my blunders are, one an intermittent a/c loss on a Suburban, the other an IAC problem on a Durango. Both of them I spent all day on and both new batteries solved the problem...lmao
I have a basic list I usually run thru and the checking the battery is at the top of it but every once in a while when "I know what it is" I'll cut to the chase........ Man why don't we ever learn.............
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Tom Greenleaf
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Jan 22, 2010, 2:42 AM
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I'm a freak about any battery that has gone dead enough to reset clock or over 3 years old myself. Amazing what a quality new one can solve.
A six month hunt on a seriously handicapped person's family Suburban for a door lock issue. Doors would always lock but wouldn't always open. Not cool when mobility aids are in the back! New battery solved it for two months and it returned?? Intermittently would work or work with engine running for months then act up once in a while. consulted and paid for more help that I was overlooking something.
Luck would have it a Springtime would come and A/C was needed and ducts wouldn't channel thru panel vents. This after the remote receiver was replaced the Fall before which is a pill up over gas pedal.
Turns out the rods for the duct work actuator were broken by another while replacing the receiving module so I while there found the relay - six prong - set of points inside (I l opened old one) for open and another for lock! Just toss it - I was there. That was the whole problem all along and was capable of draining the battery as the relay always has 12v available!
Moral is not to overlook the simple stuff sometimes. As Sidom just said it happens to all of us really only to find the silliest thing was it all along,
T
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