Parasitic Voltage Draw

Once again I’m reaching out to the Tacoma experts! When purchased this summer the truck had a new battery in it, but, if it sat for two to three weeks, the battery was dead. The battery will pass a load test fine. Started looking for a voltage drain. When I pull the OBD 7.5 amp fuse, the draw drops from 122 mA to 58mA. The kicker for me is that a Pioneer nex stereo is installed where the OEM screen was, and is connected in the OBD port. I’m trying to figure out if that’s where it should have been connected, or is there a better way. The connection looks pretty hokie/ not professional! The previous owner had it installed at a Best Buy where he purchased the stereo. Thoughts?

 

Does your radio work when the truck is turned off?

If I had a $ for every botched Best Buy install I've heard about, I could eat lunch in my favorite greasy spoon everyday for a week and have money left over.

 

Only with the key on.

 

Or no. Would be the correct answer

 

Could be connected to the OBD port because the stereo can display vehicle diagnostics - might want to Google that with your specific model.

I thought leaving my Bluetooth OBD2 reader plugged in was draining my battery but it turned out I had a bad alternator, I would make sure the battery is fully charged then get the dealer or a proper auto electrician to do an ABC check (alternator, battery and something else, it's only like a half hour labor)

 

Unplug the Pioneer radio from the obd, check the current draw, then pull the obd fuse, compare the differential from your connected measurements and disconnected readings. that should isolate the radio.

 

Ended up that there was a splitter in the OBD, with a tuner chip to one, and the stereo on the other. Pulled the splitter and chip out, the mA dropped to 58mA. I think that’s close to what it should normally read? I will Google and see what I come up with. One of these years, if, I live long enough, I’ll be able to answer someone else’s thread! Thanks for your input, sometimes a sounding board is the best help

 

IIRC, The draw should be less than 50Ma (0.050A)
And for some reason Toyota says to lock the hood latch.
Why I don’t know, but I do remember that......

@Bishop84

 

I’ll keep looking then. That was with the hood open, not sure if that will make a difference. But, I’m learning new things every day. Which beats the alternative!

 

.58ma is really close. Some vehicles take hours before all the modules “go to sleep”.
I’d wait and see what some of the Techs on here say.

 

One thing about this time of year in Colorado, if I didn’t get it, I’ll know in a few days at these temperatures. It’s not my daily driver, and probably won’t get started for a week or so.

 

0.080A after 1 hour, locked.

2 -3 weeks is too much and requires a battery tender,

 

Thanks. And Merry Christmas!

 

Did you keep checking for other parasitic draws? It sounds like you found the main culprit, but it doesn't hurt to keep checking to see if anything else is drawing power. As mentioned above I believe 58 Ma is still a little high.

 

Gave up for the evening! Heading back out this morning to see where it’s at today. I’m getting old enough to not like cold or dark as much as I did once. Is there anything that should take more than an hour to go to sleep? Any good ways to check the fuses inside the cab with the door open?

 

If you need the doors open but want the truck to think they are closed latch the latches with a screwdriver.

You have to be careful pulling fuses looking for battery drains because on modern vehicles sometimes pulling a fuse can wake up modules . Best method is to put a voltmeter set to mv across the terminals of each fuse, it should read 0, if you get a reading other than 0mv theres current going through that fuse. Here is a good video explaining parasitic draw testing.

 

Thanks, good video. I’ll try this method and see what else is drawing on the battery.

 

Well I’m getting 38mA across radio 1, and 20MA up and down To zero, then back up on ecu 1, the security system?

 

Theres always gona be a few ma of current draw on a modern vehicle, idealy should be less than 50ma but anything over 100ma is definitely too much. Sounds like your either going to have to get a different radio or use a battery maintainer which would be a good idea anyway if it's going to be sitting for weeks at a time, only other option would be to put a battery disconnect on it and leave it disconnected when not in use.

 

I’m considering a battery minder, as the stereo system is something the wife is pretty set on. Not sure what else can be done with it. I’ve considered getting an OEM screen to see what difference that would make. A little pricey. The amp doesn’t seem to be pulling anything, but, the stereo definitely is.