05 tahoe 05 Tahoe battery drain!

Sara Mae Highfield · December 30, 2018

Okay so I don’t know anything about vehicles just looking for advice. I have a 05 Chevy Tahoe z71 with 200,000 miles. In the last 6 months it’s been in the shop more than not and when it’s not in the shop it won’t start. Nobody can find the problem. I’ve had 3 different brand new battery’s on it and 4 alternators. In 6 months. It also has a new instrument cluster that was put in about a month ago. With a lot more things done. I’m just not sure what. I just know it’s been expensive. But still if I leave it sitting for more than an hour or two, the battery is dead and I have to jump it off. I’ve learned that if I unhook the battery cable, it will last for around 12 hours but after that. Dead. The mechanic said there was a short because sometimes all the interior lights won’t come on, only the front and very back, the middle won’t come on or if you open a certain door none of the lights come on... but still the problem can’t be found. Any advice on what to suggest to look for? I’ve had it almost 4 years and it’s been a good vehicle until this happened! Please help!

sefiroxx · December 31, 2018

Throwing parts at the problem is an expensive outing.

1st: problem definition:
- car won't start
- battery drain
- other passenger electrical

2nd: Diagnostics:
a) starting
- assuming the engine does not crank at all:
- controls for the starter include ignition switch, security, neutral safety switch (has to be in park or neutral), fuse, relay, starter solenoid, starter.
- You can bypass nearly all of the above at the starter. It is directly connected to the battery and a second wire through all of the above items. Use a jumper wire and connect the two posts together. It attempts to crank, then you have a problem with the other controls. If it does not crank, then starter is bad
- to diagnose the other components, you will need a meter to backtrace the control wire to see where the signal is present or not
- simple check for the relay is switch out with another one in the electronic/fuse box

B) battery drain
- it drains while not connected? Something changed from the shop storage to installing. If the battery, new is installed with no cable hookup, would it drain? It shouldn't. How are you testing?
- normally to test, a test light or amp meter is hooked up between the battery and the battery cable. It will show drain. Then start pulling fuses until the drain stops. The last fuse pulled will indicate which circuit to research
- if you suspect the alternator, these can be tested at the local parts shop. I doubt it's the alternator.

C) other electrical
- typically the hardest to find.
- in your case, a whole section of the passenger compartment is going out , this would point to a common item. Ignition switch, body control module, fuse, or ground.
- ground connections are typically located behind the dash on the outer edges, on the driver side floor usually 6 inches up the b pillar (that which the back seat driver side door is mounted to) and somewhere in the rear passenger area
- work on a and b and you might find the the answer to c as well

Finally
I had a similar problem. My Sierra symptoms included a random inability to start. Did the standard check on control points including ignition switch, battery etc. Eventually found:
- stater had a dead spot on it. But turning the key a half dozen times would jar it enough to turn the dead spot away
- ignition key cylinder is so worn that it can be turned just enough (without a key) to turn engage the "run" state which is a high battery drain. I can see this state on the dash - battery lit and the PRNDL symbol is dimmly lit

Hillwood · December 31, 2018

Okay so I don’t know anything about vehicles just looking for advice. I have a 05 Chevy Tahoe z71 with 200,000 miles. In the last 6 months it’s been in the shop more than not and when it’s not in the shop it won’t start. Nobody can find the problem. I’ve had 3 different brand new battery’s on it and 4 alternators. In 6 months. It also has a new instrument cluster that was put in about a month ago. With a lot more things done. I’m just not sure what. I just know it’s been expensive. But still if I leave it sitting for more than an hour or two, the battery is dead and I have to jump it off. I’ve learned that if I unhook the battery cable, it will last for around 12 hours but after that. Dead. The mechanic said there was a short because sometimes all the interior lights won’t come on, only the front and very back, the middle won’t come on or if you open a certain door none of the lights come on... but still the problem can’t be found. Any advice on what to suggest to look for? I’ve had it almost 4 years and it’s been a good vehicle until this happened! Please help!

You stated that you know nothing about vehicles.. Thanks for being honest..
Any friends who could help?
Try and find a repair shop that has good reviews.. Sounds like the one you have is not helpful..
This is my recommendation.

Sent from my SM-G965U using Tapatalk

The Zip · December 31, 2018

You’ve had the truck for 4 yrs and within the last 6 months something changed, what changed electrically? Don’t think your batteries or alternators were bad. Your receipts should show if your mechanic conducted an electrical diagnosis on the first visit. If not, have an electrical diagnosis done, this may not tell you what is causing the drain, but it might tell you what is not causing it (like new batteries or alternators). A reputable shop would not have allowed you to purchase 3 batteries and 4 alternators within a 6 month period.

Ak_grown · January 1, 2019

too many different options to go with, but simple one i would say, check the battery cables, sounds like a loose cable to battery, easy to strip bolts that hold cables tight. a loose cable can kill battery. the cables should not be able to twist/rotate when connected to battery.

could be an issue with the new cluster not shutting down the BCM(computer) which will drain the battery while it sits over night. a Digital multimeter can help track down issue but you need to be familiar with it.

i honestly think is something simple, but i like to trouble shoot electrical issues.

GMinTN · March 23, 2021

On 12/30/2018 at 4:26 PM, Sara Mae Highfield said:

Did you ever get it figured out? I am having a very similar problem in my 2005 Tahoe. The radio and gauges are staying lit even after I take the key out, battery drained overnight as well.

GMinTN · March 23, 2021

On 12/31/2018 at 2:59 PM, sefiroxx said:

Throwing parts at the problem is an expensive outing.

1st: problem definition:
- car won't start
- battery drain
- other passenger electrical

2nd: Diagnostics:
a) starting
- assuming the engine does not crank at all:
- controls for the starter include ignition switch, security, neutral safety switch (has to be in park or neutral), fuse, relay, starter solenoid, starter.
- You can bypass nearly all of the above at the starter. It is directly connected to the battery and a second wire through all of the above items. Use a jumper wire and connect the two posts together. It attempts to crank, then you have a problem with the other controls. If it does not crank, then starter is bad
- to diagnose the other components, you will need a meter to backtrace the control wire to see where the signal is present or not
- simple check for the relay is switch out with another one in the electronic/fuse box

B) battery drain
- it drains while not connected? Something changed from the shop storage to installing. If the battery, new is installed with no cable hookup, would it drain? It shouldn't. How are you testing?
- normally to test, a test light or amp meter is hooked up between the battery and the battery cable. It will show drain. Then start pulling fuses until the drain stops. The last fuse pulled will indicate which circuit to research
- if you suspect the alternator, these can be tested at the local parts shop. I doubt it's the alternator.

C) other electrical
- typically the hardest to find.
- in your case, a whole section of the passenger compartment is going out , this would point to a common item. Ignition switch, body control module, fuse, or ground.
- ground connections are typically located behind the dash on the outer edges, on the driver side floor usually 6 inches up the b pillar (that which the back seat driver side door is mounted to) and somewhere in the rear passenger area
- work on a and b and you might find the the answer to c as well

Finally
I had a similar problem. My Sierra symptoms included a random inability to start. Did the standard check on control points including ignition switch, battery etc. Eventually found:
- stater had a dead spot on it. But turning the key a half dozen times would jar it enough to turn the dead spot away
- ignition key cylinder is so worn that it can be turned just enough (without a key) to turn engage the "run" state which is a high battery drain. I can see this state on the dash - battery lit and the PRNDL symbol is dimmly lit