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good thread here. I've never had starting issues, but even on battery number 2 my charge has never held long and it just never felt right. Just a 1 winter month in 10 years and always garage kept. I want to check this out tonight but have one question:

can you tell from the bolt head if it's corroded, or would I have to remove and inspect the exposed threads? Reason I'm asking is if everything looks good from up top, I see no reason to risk snapping bolt head off top unless I really need to have it off to inspect the whole setup. if that makes sense...
 

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good thread here. I've never had starting issues, but even on battery number 2 my charge has never held long and it just never felt right. Just a 1 winter month in 10 years and always garage kept. I want to check this out tonight but have one question:

can you tell from the bolt head if it's corroded, or would I have to remove and inspect the exposed threads? Reason I'm asking is if everything looks good from up top, I see no reason to risk snapping bolt head off top unless I really need to have it off to inspect the whole setup. if that makes sense...
You can see the bottom of the bolt if you lay down and look up inside the back bumper. I don't have a pic, but if you look at it from the top (battery compartment) and get an idea where the bolt sits, it should be pretty obvious that you're looking at the right one from the bottom.

I changed mine, and it was quite rusty. I don't think it will be so bad you won't be able to back it out easily.

If you don't already have it, get an M8x1.25 (pretty sure that's right) tap and clean up the threads of the hole before installing a new bolt.
 

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Battery ground bolt should be inspected from the thread side since this portion is exposed to the various climatic conditions i.e. weather elements. Anecdotally, it would be more of an issue if the underside of the car is or has been frequently exposed to salt, road ice prevention treatment, etc.
 

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thanks guys, that's what i assumed it's just that there were so many comments about "just lift up your trunk carpet". I'll take a gander this weekend and report back. Maybe I'll see if I can get some pics for members to reference.
 

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Grounds have been vexing car owners for years. My first new car, an '83 GTI, started having electrical gremlins. I got through to an engineer at VW in Troy, MI and he told me the transmission was grounded to the body - but the engine was not and they had problems with corrosion between iron block and aluminum trans case. I had one of the guys at the plant make me a short braided plated copper welding ground strap with soldered ends and holed drilled in each end, attached it between the cylinder head and trans case - problem solved.
 

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Good info! I checked mine and it looked great but twice a year I soak my under body with WD40 and it works well to keep things coated and lubricated. A old mechanic told me to do this to my F150 back in the early 2000's and I have been doing this ever since to all my vehicles. It's seems to help keep bushings softer longer and helps bolts come off easier under the bottom.
 

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For sure the next thing I am checking i replaced multiple alternators chasing the problem spikes up to 15.5 volts and drops into the low 12's according to the dash gauge atleast
 

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From GM's description of the charging system:

The engine control module (ECM) controls the generator through the generator turn ON signal
circuit. The ECM monitors the generator performance though the generator field duty cycle signal
circuit. The signal is a pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0–100
percent. Normal duty cycle is between 5–95 percent. Between 0–5 percent and 95–100 percent
are for diagnostic purposes. The following table shows the commanded duty cycle and output
voltage of the generator:

Commanded.............Generator
Duty Cycle..................Output Voltage
10%............................11.00 V
20%............................11.56 V
30%............................12.12 V
40%............................12.68 V
50%............................13.25 V
60%............................13.81 V
70%............................14.37 V
80%............................14.94 V
90%....................15.50 V

The generator provides a feedback signal of the generator voltage output through the generator
field duty cycle signal circuit to the ECM. This information is sent to the body control module
(BCM). The signal is PWM signal of 128 Hz with a duty cycle of 0–100 percent. Normal duty cycle
is between 5–99 percent. Between 0–5 percent and 100 percent are for diagnostic purposes.
 

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Well I was concerned with the voltage but if that is normal the only other thing is randomly shutting off sometimes. It has loads of aftermarket parts as well
 
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