Diagnosing parasitic drain

Makes sense!

With what you were saying before - if I have the leads in the A and COM want to measure mA you have to go past volts on the dial. Should the leads not be connected to anything when moving the dial so it doesn't try to read for that milli-moment or should that not be a problem?

 

Looks like this one was set to AC, might check it again on DC.

 

Volts should be fine, that puts the meter in a very high resistance state that is really hard to break (which is why you can plug it into a house wall socket and it doesn't break anything)

The one to watch out for is the current side, since the meter is in a very low resistance state to read current and so any voltage across it will only be limited by the resistance in the circuit its connected to. So in the case of a big car battery, there's tons of current capacity available and it'll eat fuses all day.

 

Thanks. I was hopeful for a moment but reads the same on DC.

That makes a lot of sense. Thanks for your help! New fuses are on the way

 

Replaced all the DMM fuses and guess what - it works! So first picture is of the truck awake 1.753 A. Second picture is it asleep after 1hr at .01 A.

So... nothing is pulling power above normal power when it is asleep. What would cause battery drain then? Bad battery cables, bad ground somewhere?

I do get an intermittent p0441 and p2420 every now and again - maybe they are inter connected?

 

Whats the voltage with the engine running? Have you had the alternator tested?

 

New fuses make everything better! It's possible that those evap codes are the problem; maybe the vent vv or purge solenoid are going into spasm. I have an intermittent problem with my wife's Mustang; every now and then it will go into a random parasitic drain, and sets a code for "Dome light dead short". I have metered, meggered, and inspected every inch of the circuit but can't find the cause of the problem. TBH, a .011amp draw is actually a little lower than I would expect. I've never measured my Tacoma, but I would have expected a 'resting' draw of more like 0.025 - 0.030.

 

I would think bad alternator.

 

Yeah its like almost 14v so I know the alternator is working.

Yeah I changed the gas cap to an OEM one and purge solenoid (not OEM so might try one of those). Its probably connected.

Same! I was surprised how low it was I too was expecting about 25-30. I'm going to try it again to see if I get the same result.


Electrical is so much fun!

 

Tried it again with different method and getting the same result. I’m going to leave it hooked up for about 30 minutes and see what the min and max value is. Maybe something drawing power every now and then

 

Max so far is .025. Well in range of ok

 

Max was .025 with avg .012 over an hour. Did not witness a spike. I would think I would after that amount of time but what do I know?

 

Don't know specifically for our Toyotas, but, getting the system into sleep mode and breaking into the circuitry correctly such that you can measure current the way your doing can be anything but straight forward for some vehicles. The act of disconnecting the battery can change states of things within elec system. Watch the video toward the front of this thread and maybe try that method, should be very quick/easy. This method is cool because you do not have to break in/disturb the system in any way. Hook everything up. Shut all doors except the drivers. Manually latch the drivers door while it is open. Turn the truck off, wait an hour and start back probing the fuses for voltage. Set the meter for DC Volts. You are looking for anything not 0 volts. Volts across the fuse implies current flow. V=IR, I=V/R. If you find voltage due the math to determine current. Use extra fuses, or pull and measure the resistance of various sizes to determine R for the math. Check both under hood and in cab fuses.