Battery Drain
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From: Elk Grove Califormia
Battery Drain
My 2005 Convertible has been tough on batteries since purchased in 2011 with 8500 miles, it now has 112K. It was manageable when I drove it daily, because of COVID, I now work from home so the car goes 3-4 days without driving anywhere. When turned off the current drain is normal (0.3A) so techs have not been able to find the problem. When the car sits for more than a day, the battery will be drained. I stuck an inductive amp meter on it and checked it overnight. The next day the drain was 1.2A , when fuse 12 was pulled the drain went back to normal. The owners manual shows fuse 12 is the odd numbered fuel injectors. I would love to hear any ideas on how to replace the board that controls the odd numbered fuel injectors.
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From: Cape Coral, Florida
Bob, WELCOME to the Forum !!...yes, fuse 12 controls the odd injectors but the injectors are "ground side switched"...the ECM is controlling the ground to fire the injectors so it wouldn't be an ECM board issue...power for the injectors is through relay 44 I believe...power for the injectors is absent with the car off...you sure you have the right fuse ??...,now the injector driver could be stuck closed but as long as there is no power to the injectors they won't fire...if you had power to the injectors the fuel would flood the cylinder of whichever injector driver is stuck closed.
Le Mans Master
Joined: Dec 2004
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From: West coast CA
My 2005 Convertible has been tough on batteries since purchased in 2011 with 8500 miles, it now has 112K. It was manageable when I drove it daily, because of COVID, I now work from home so the car goes 3-4 days without driving anywhere. When turned off the current drain is normal (0.3A) so techs have not been able to find the problem. When the car sits for more than a day, the battery will be drained. I stuck an inductive amp meter on it and checked it overnight. The next day the drain was 1.2A , when fuse 12 was pulled the drain went back to normal. The owners manual shows fuse 12 is the odd numbered fuel injectors. I would love to hear any ideas on how to replace the board that controls the odd numbered fuel injectors.
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From: Cape Coral, Florida
Yes, fuse powers both injectors and coil packs but I don’t see how a coil pack can cause a parasitic drain with the engine off ??…if coil power wire would short to ground I would expect to see the fuse blow and not kill the battery.
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From: Illinois
As the voltage on the battery drops, funny things can happen in the engine control. It is not supposed to happen. It sounds to me like the ECM is getting confused, as the voltage slowly drops, and turning on items that should not be enabled when the car is off.
Check the battery voltage when you see this happening. I bet it is less than 12.5 volts.
This is why so many people use battery tenders, to prevent this kind of thing from happening.
Check the battery voltage when you see this happening. I bet it is less than 12.5 volts.
This is why so many people use battery tenders, to prevent this kind of thing from happening.
Melting Slicks
Joined: Jun 2005
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From: Sicamous BC
Maybe chase the .3a draw, that is to high. Possibly the high draw of 1.2a is connected to the .3ah
.3ah is 7.2a per day, depending on battery size that will take it down to 50% within a few days
.3ah is 7.2a per day, depending on battery size that will take it down to 50% within a few days
Retired & lovin' it!
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From: Jackson NJ
You don't say if your '05 if manual or auto, but being an '05 manual owner since new, I can tell you that these cars must be shut down in Reverse in order to avoid parasitic drain. Matter of fact, the '05's originally came with a warning tag on the shifter, reminding drivers to shift to Reverse when shutting down. Likewise, a battery tender (not a charger) is necessary to protect battery life if the vehicle is parked for more than 3 or 4 days. If it's an auto, can't help you.
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From: Elk Grove Califormia
Correction, it is Fuse 11 that causes the drain. My current meter must take a couple seconds to drop off, so I had moved to 12 before I saw the drop. I repeated the fuse pulls after catching the car in the same excess drain again. Taking some time with each fuse out I was able to identify fuse 11 which makes more sense. This is the Engine Control, Transmission Control, Easy Key modules. Where is this module located?
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From: Elk Grove Califormia
It is manual, the car is in reverse when the drain occurs. The car always reads 0.3A when shut off. It is some hours later the drain jumps to 1.2A and I have identified the fuse carrying the current is fuse 11 (not 12 as originally thought).
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From: Elk Grove Califormia
A couple days would be great, This can happen overnight. I now leave it on a battery tender at night. That is how I was able to catch it before the voltage dropped to low to believe anything was working properly. There is something waking up after the car has been turned off for a few hours, maybe a day or two, it is random. I see the current draw go from 0.3A to 1.2A. Something on Fuse 11 is randomly waking up and draining the battery. There are 3 modules on this fuse, How do I take the next step to figure out which one or are all 3 in the same replaceable module?
Le Mans Master
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St. Jude Donor '17
https://www.motortrend.com/how-to/ve...-new-corvette/
Fuse 11 powers the red/white wire to the power train control module, transmission control module, remote control door lock receiver
Turn off the keyless entry setting as a test
Fuse 11 powers the red/white wire to the power train control module, transmission control module, remote control door lock receiver
Turn off the keyless entry setting as a test
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From: Elk Grove Califormia
I agree, something is getting confused. I leave it on a battery tender now when it is in the garage. I still see the 1.2a draw when connected to the battery tender, so it is not low voltage causing it, but either the EMC or Transmission control, or easy mode entry is turning something on. Any thoughts on which to replace 1st?
Le Mans Master
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St. Jude Donor '17
I had an issue with amp draw.
Pull battery cables off, touch them together, Pull every relay on fuse box and inspect for burn marks, clean contacts. Use a battery terminal cleaner on the posts, clean inside battery cable clamps.
You may need to pull up your seats by the bolts a bit and reach in and unplug and clean contacts on the box under them.
I took apart my fuse box all 3 layers, cleaned all contacts with the red bottle electric contact cleaner. Removed oxidation on pins.
Clean all ground points. I installed https://www.saccitycorvette.com/C6-Big3.html which improved ground wire connections.
My issue ended up being the alternator causing an internal ground.
Most likely you have a ground issue and relay that is staying stuck open.
Pull battery cables off, touch them together, Pull every relay on fuse box and inspect for burn marks, clean contacts. Use a battery terminal cleaner on the posts, clean inside battery cable clamps.
You may need to pull up your seats by the bolts a bit and reach in and unplug and clean contacts on the box under them.
I took apart my fuse box all 3 layers, cleaned all contacts with the red bottle electric contact cleaner. Removed oxidation on pins.
Clean all ground points. I installed https://www.saccitycorvette.com/C6-Big3.html which improved ground wire connections.
My issue ended up being the alternator causing an internal ground.
Most likely you have a ground issue and relay that is staying stuck open.
Le Mans Master
Joined: Oct 2012
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From: Out back
I always thought the power drain was caused by the passive FOB monitors never turning off. I just run a battery tender to a magnetic plug (like on the exotics) and I never run into battery issues. This has been a known issue for decades, why fight it? Just put a tender on it and be done.
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From: Cape Coral, Florida
I always thought the power drain was caused by the passive FOB monitors never turning off. I just run a battery tender to a magnetic plug (like on the exotics) and I never run into battery issues. This has been a known issue for decades, why fight it? Just put a tender on it and be done.
Le Mans Master
Joined: Oct 2012
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From: Out back
Except when it's a passive system that you can't turn off...just sayin'. How can anyone tell how much parasitic drain is too much parasitic drain?
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From: Cape Coral, Florida
That is why all modern cars have some kind of parasitic drain to take into account those “passive” modules…the drain for any car is sometimes in service info or “rule of thumb” is the reserve capacity of the battery divided by 4….100 minute reserve capacity drain would be around 25 milliamps.
Last edited by C5 Diag; Nov 7, 2022 at 12:11 PM.
Melting Slicks
Joined: Apr 2019
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From: Northern Wisconsin
That is why all cars have some kind of parasitic drain to take into account those “passive” modules…the drain for any car is sometimes in service info or “rule of thumb” is the reserve capacity of the battery divided by 4….100 minute reserve capacity drain would be around 25 milliamps.