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Discussion Starter #1 (Edited)
Hello all. I am a new member here. I own a 2008 Nissan Altima 2.5L with 154k miles on the body, 103K miles on the tranny/engine. Just replaced the engine and transmission and have run into a battery draw issue. I am not sure if this was happening before, since I don't ever remember having an issue with the battery dying. The alternator went out on my a while back but once that was replaced I didn't have any issues.

So I noticed my battery dying and decided to find out what was causing it. I charged the battery, it was at 12.9-13v when beginning the test. I put the positive lead on, made sure there is no corrosion, and latched it tight. I connected my multi-meter, set at the 10A-DC setting, to the negative lead, then the to the negative battery terminal. Initial load was .560a then instantly dropped to about .435a. After about fifteen seconds it dropped to .230a. After one minute, the amperage was at a steady .150a. I started testing out the fuses. I ran into one that caught my eye, and dropped the amps to .090a (which is normal from what I hear?).

The fuse that I took out was a 10A fuse, controlling the 'ROOM LIGHT'. All my doors were closed, there were no lights on anywhere in the vehicle, especially not in the interior. I turned the dome light on, after putting the fuse back in, and it clearly drew more than .150a. Turned it off, and it went back to .150a. I set it to completely off, and still the same thing.

Has anyone had any weird issues like this? Nothing seems to be on at all, yet there is a clear EXTRA 50-60mA draw. Without the ROOM LIGHT fuse, I am down to .090a. I doubt replacing an engine would cause this.. but what do I know at this point. Any advice on this?
 

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Sup Mod keeping the peace
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If the electrical system is drawing 50mAmp with the vehicle completely shut off, that's normal in late model computer controlled vehicles. When the vehicle is shut off, the ECU, IPDM, and TCM are in "sleep" mode so they are still drawing a very small amount of current.
 

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Sup Mod keeping the peace
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During your engine/trans replacement, it's possible that a wire got pinched causing the extra draw. If you don't have a copy of the Factory Service Manual (FSM), you can get one from: https://ownersmanuals2.com/. Sections EXL.PDF, PG.PDF, MWI.PDF, INL.PDF, PWO.PDF are the ones you need to use. With the battery (-) cable disconnected, unplug the ECU, TCM, IPDM to start off with to test your current draw since they are close to the engine and may have been hit during engine replacement. Good luck to your search.
 

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Discussion Starter #5 (Edited)
During your engine/trans replacement, it's possible that a wire got pinched causing the extra draw. If you don't have a copy of the Factory Service Manual (FSM), you can get one from: https://ownersmanuals2.com/. Sections EXL.PDF, PG.PDF, MWI.PDF, INL.PDF, PWO.PDF....
This is AMAZING! Thank you so much! I will post my findings here when I get down to it. Currently I am popping the fuse out and rolling along without it. Do you by happenstance know what components are drawing from the battery when the vehicle is off and just sitting there? Is it just the ECU/TCM?

Now to figure out how to read these and apply them...
 

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Sup Mod keeping the peace
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There's a GI.PDF section in the FSM that explains the various wire color codes, symbols, definitions, connector types, and so on. You also might be interested in downloading section LAN.PDF which explains the various inter-connects between the intelligent components; it might help in your hunt for the bad guy.

The other components that might be drawing power are the IPDM and the BCM.
 
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