2009 Toyota Venza draining battery

my 2009 venza it draining the battery I check alternator it ok what can it be?

Parasitic drain from some electrical component. Replacement radios, aftermarket remote starters or security systems are prime targets for this.

The trouble could be caused by a number of things. If you want to solve the trouble yourself then you will have to check things out to pin down the problem area. Here is a link that should help you.


I sure hope this isn’t still the original battery?

If so, I wouldn’t expect it to be in good shape . . . very old batteries often can’t be relied on

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Do the easy stuff first. Make sure the battery is good via a load test, and fully charged. Park the car and turn it off, close all the doors, wait 1/2 hour. Easier if you do this at night in a dark area. Are the brake lights still on? Are any exterior lights still on? Any interior lights that you can see looking through the window still on? If not, then open the door make sure the interior lights you can’t see are turning off. Glove compartment, under the hood, trunk, etc. Also make sure the battery case is clean. If the battery case has any acid on it, that can act as a conductor & cause a drain current directly from the pos to neg post, across the case. If nothing above found …

Ask your shop to measure the parasitic drain current with everything turned off. If it is 50 mA or less, there’s no excessive battery drain. If it measures considerably more than 50 mA, say 1000 mA, the common way to figure the cause is to remove fuses one by one until it returns to less than 50 mA. At that point you’ll know which circuit it is, and once narrowed down to the circuit it is usually pretty easy to figure out what device is causing it. A very common cause for battery drains is the alarm system, especially aftermarket systems, so double check that. Aftermarket radios are the next most common. Sometimes the alternator itself can drain the battery, bad alternator diode; so if none of the fuses seem to stop the drain, disconnect the alternator, see if that helps.

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