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Old 06-14-2021, 01:34 AM   #1
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Drives: 2010 Toyota yaris
Join Date: Jun 2021
Location: CA
Posts: 1
Parasitic draw/drain


First off this Toyota is my wife's car and im use to working on my older trucks (76 Cheyenne w/454 and 86 silverado w/379 diesel) that being said, im not really the best at electrical issues with newer stuff.

Basic background of the issue and what lead me to here:

The car had been running fine and then one night she forgets that she had her key in accessory, few hours later and the battery is dead. I go and jump start the car, let it run for 10 minutes or so and call it a day. In the morning the battery is dead again, had the battery tested and replaced since it was defective.

But i still had a hunch this was bigger than just a battery issue, i tested the alternator output and it came to about 13.8-14 (alittle low i think) and then i tested for a parasitic draw.

Thats where im alittle fuzzy, dc current doesnt really change that much from vehicle to vehicle so i did this test the same way i always do it. Pop the negative lead off the terminal and hook up the multimeter to each end of the negative side, when i do that it reads 11.8-12.1 volts. So correct me if im wrong but this is not how the yaris should read.

To try and find the issue or location without wire chasing, i test the tops of the fuses and see what they say (with battery installed). Everything was pretty low except the abs1/vsc1 fuse. I pulled it out to check the posts and it was reading 12ish volts.

The part that confuses me is with that fuse pulled and then i do the draw test again i still get the same reading as before. So im not sure if its an issue prior to the fuse box or what any help would be appreciated 🤙
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Old 06-14-2021, 07:37 AM   #2
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Drives: '08 2zr swapped Vios M/T
Join Date: Oct 2012
Location: Caledonia Ont.
Posts: 2,912
When ever I've chased a parasitic draw, I have always read amperage off the battery when wiring a dvm inline.

Amperage is way easier as you don't have to convert voltage to amperage to see what draw you are getting. Once you have established a base draw start unplugging various fuses and see what causes the amp draw to drop. That circuit will have your problem on it.

From there you'll want to access a wiring diagram of that circuit to better narrow own your problem.

Btw 13.8-14v is completely normal off the alternator. It wouldn't hurt to throw a charger on the battery to get it up to a full charge then test for a draw as well as a proper load test on it to rule out a potential battery issue. I know it's new but they rarely come fully charged from the store.
No one ever wants to give a Yaris the point by...
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Old 06-15-2021, 07:33 AM   #3
Drives: 2007 Yaris Sedan
Join Date: Apr 2009
Location: CT
Posts: 239
Your car will always have some current draw.
The ECM and other devices have a small current draw. To do things like remember the setting in your radio and ECM settings. Power the power locks and security system if you have them.
Measuring by the voltage method will not work as the small current draw will give you false voltage readings.
Use the current method already mentioned.
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drain, electrically challenged, parasitic draw, toyota, yaris

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